利拉鲁肽对2型糖尿病大鼠降血压、利水盐的作用机制探讨

摘要

Objective To observe the effects of glucagon like peptide-1 (GLP-1) analogues liraglutide on expressions of nitric oxide synthase (NOS) and cyclo-oxygen-ase (COX)2 in renal medulla of type 2 diabetes rats, and the mechanism of its lowering blood pressure and promoting excretion of water and salt in kidney. Methods Type 2 diabetes model rats were generated by high-fat and high-sugar feeding for 8 weeks followed by intraperitoneal injection of streptozotocin (STZ). Subse⁃quently, eighteen type 2 diabetes rats were divided into two groups: liraglutide treatment group (DMT) and diabetes group (DM). Twelve normal rats were divided into two groups: liraglutide treatment wild type group (WTT) and wild type group (WT). DMT and WTT groups were given liraglutide (200μg/kg) by subcutaneous injection, DM and WT groups were given equivalent normal saline by the same way. The levels of blood glucose and blood pressure were detected at 0, 2, 4 and 6 weeks after treatment in groups of rats. Samples of urine were collected for detecting ion concentrations (K+, Na+and Cl-) af⁃ter treatment for six weeks. Rats were sacrificed and blood samples were collected for detecting ion concentrations (K+, Na+and Cl-). The expression levels of NOS and COX2 mRNA and protein in renal medulla were detected by real-time PCR and Western blot assay. Results After treating with liraglutide, the values of blood glucose (F=5.933, P<0.05) and blood pres⁃ sure (F=22.070, P<0.05) were gradually decreased in DMT group. After treatment with liraglutide for 6 weeks, the values of blood glucose (mmol/L:12.78 ± 3.82 vs. 18.75 ± 1.68) and blood pressure (mmHg:119.98 ± 4.43 vs. 136.42 ± 4.48) were signifi⁃cantly decreased (P<0.05) in DMT group than those of DM group (P<0.05). There were no significant differences in the concentrations of K+, Na+and Cl-between the two groups. There were higher levels of K+(mmol/L:46.55 ± 6.43 vs. 33.13 ± 9.71), Na+(mmol/L:56.33±8.83 vs. 41.20±7.25) and Cl-(mmol/L:159.81±25.06 vs. 71.44±12.99) in urine in DMT group than those of DM group (P<0.05). The mRNA levels and protein expressions of NOS and COX2 in renal medulla were significant⁃ly increased in DMT group than those of DM group (P<0.05). Conclusion GLP-1 analogues liraglutide may enhance the expression of COX2 by increasing the expression of NOS to excrete water and salt, and decrease blood pressure.%目的：通过观察胰高血糖素样肽-1（GLP-1）类似物利拉鲁肽对2型糖尿病大鼠肾脏内髓一氧化氮合酶（NOS）、环加氧酶2（COX2）表达的影响，探讨利拉鲁肽降血压和利水盐的作用机制。方法30只雄性SD大鼠给予高糖高脂饲料喂养，自由摄水，8周后空腹注射链脲佐菌素（STZ），成功建立2型糖尿病大鼠模型18只，选取12只随机分为利拉鲁肽处理2型糖尿病模型（DMT）组和2型糖尿病模型（DM）组，另取12只正常大鼠随机分为利拉鲁肽处理野生型大鼠（WTT）组和野生型大鼠对照（WT）组，每组6只。DMT和WTT组每天予以利拉鲁肽（200μg/kg体质量）皮下注射，DM和WT组每天予以等量生理盐水皮下注射，各组分别在给药后0、2、4、6周检测血糖和血压，给药后6周收集尿液检测K、Na、Cl离子浓度，然后处死大鼠，收集血液检测血K、Na、Cl离子浓度，取肾组织通过Real-time PCR和Western blot检测肾脏内髓NOS和COX2的mRNA和蛋白表达水平。结果利拉鲁肽干预后，DMT组大鼠血糖（F=5.933，P<0.05）及血压（F=22.070，P<0.05）随时间变化逐渐降低。在干预6周后，DMT组大鼠血糖（mmol/L：12.78±3.82 vs.18.75±1.68）和血压（mmHg：119.98±4.43 vs.136.42±4.48）较DM组均明显降低（P<0.05），血液中K、Na、Cl离子浓度与DM组相比无明显差异，但尿液中K（mmol/L：46.55±6.43 vs.33.13±9.71）、Na（mmol/L：56.33±8.83 vs.41.20±7.25）、Cl（mmol/L：159.81±25.06 vs.71.44±12.99）离子浓度高于DM组大鼠（P<0.05），且肾脏内髓NOS、COX2的mRNA和蛋白表达均高于DM组大鼠（P<0.05）。结论利拉鲁肽可能通过NOS诱导COX2的表达增强，发挥利水盐、降血压的作用。