番茄红素对糖尿病模型大鼠肾损伤的治疗及血管紧张素转换酶的作用

目的观察番茄红素对糖尿病性肾病的治疗作用及其可能的作用机制。方法采用高糖高脂饮食加链脲佐菌素法制备2型糖尿病大鼠模型。2型糖尿病大鼠分别ig给予番茄红素5,10和20 mg.kg-1每天1次,连续8周。8周后取尾尖血用罗氏血糖仪测定空腹血糖(FBG)含量,腹主动脉采血后分离血清和血浆,用全自动生化分析仪测定血清肌酐(Scr)、尿素氮(BUN)和24 h尿蛋白(UP)含量,放免法检测血浆胰岛素(Ins)、血管紧张素Ⅱ(AngⅡ)和肾组织AngⅡ含量。HE染色观察肾组织病理形态的变化,RT-PCR法检测肾组织血管紧张素转换酶(ACE)和ACE2 mRNA的表达,Western印迹法检测肾组织ACE2蛋白的表达。结果与正常对照组相比,模型对照组FBG,Ins,Scr,BUN,AngⅡ和24 h UP含量均明显升高(P<0.05);与模型对照组相比,番茄红素10和20 mg.kg-1组Scr,BUN,AngⅡ和24 h UP含量均显著降低,Scr由(54.2±4.3)μmol.L-1分别降低到40.3±2.0和(34.4±3.8)μmol.L-1,BUN由(17.7±2.3)mmol.L-1分别降低到15.5±1.2和(13.1±0.5)mmol.L-1,血浆中AngⅡ由(858±56)ng.L-1分别降低到680±62和(623±64)ng.L-1,肾组织AngⅡ由(19.8±2.9)ng.g-1分别降低到16.7±2.6和(13.6±2.4)ng.g-1蛋白,24 h UP由(16.4±3.5)mg分别降低到13.7±1.9和(9.9±2.3)mg(P<0.05)。与正常对照组相比,模型对照组ACE2,ACE mRNA和ACE2蛋白表达水平显著降低(P<0.01),与模型对照组相比,番茄红素5,10和20 mg.kg-1组ACE2 mRNA和蛋白表达水平则显著升高(P<0.05),其中番茄红素20 mg.kg-1组效果更为明显(P<0.01);ACE mRNA表达水平与模型对照组无明显差异。结论番茄红素能降低糖尿病模型大鼠蛋白尿,改善肾功能,减轻肾组织病理变化,增强肾组织ACE2 mRNA和蛋白的表达,提示番茄红素对糖尿病性肾病的治疗作用可能与抑制肾局部肾素-血管紧张素系统的途径有关。

Therapeutic effect of lycopene on kidney injury in diabetic model rats and role of angiotensin converting enzyme

OBJECTIVE To investigate the therapeutic effect of lycopene on kidney injury in diabetic model rats and its possible mechanism. METHODS The type 2 diabetes rat model was prepared by high-carbohydrate and high-fat diet, and streptozotocin (STZ) ip given. Then the diabetic rats were ig given lycopene 5, 10, and 20 mg·kg^-1, respectively, once daily, for 8 weeks. The concentration of fasting blood glucose (FBG) was determined by Roche blood glucose meter. Serum and plasma samples were taken from the abdominal aorta before the concentration of serum creatinine (Scr), urea nitrogen (BUN), and 24-hour urine protein (UP) was determined by an automatic biochemical analyzer. The concentration of plasma insulin (Ins) and angiotensinⅡ (AngⅡ) in plasma and renal tissue was measured by radioimmunoassay. The pathological changes of renal tissue were observed by HE staining. Expressions of angiotensin converting enzyme (ACE) mRNA, ACE2 mRNA and ACE2 protein in renal tissue were measured by RT-PCR and Western blotting, respectively. RESULTS Compared with normal control group, the concentration of FBG, Ins, Scr, BUN, AngⅡ and UP in model group was all significantly higher (P<0.05, P<0.01). Compared with model group, Scr, BUN, AngⅡ and UP in lycopene 10 and 20 mg·kg^-1 groups were greatly decreased (P<0.05). Compared with model group, Scr in lycopene 10 and 20 mg·kg^-1 groups decreased from 54.2±4.3 to 40.3±2.0 and (34.4±3.8) μmol·L^-1, respectively. BUN from 17.7±2.3 to 15.5±1.2 and (13.1±0.5) mmol·L^-1, plasma AngⅡ from 858±56 to 680±62 and (623±64)ng·L^-1, AngⅡ in renal tissue from 19.8±2.9 to 16.7±2.6 and (13.6±2.4)ng·g^-1 protein, UP from 16.4±3.5 to 13.7±1.9 and (9.9±2.3)mg (P<0.05). The expression of ACE mRNA, ACE2 mRNA and ACE2 protein in model group greatly decreased compared to normal control group (P<0.01). ACE2 mRNA and protein levels in lycopene 5, 10, and 20 mg·kg^-1 groups were obviously up-regulated (P<0.05) especially in lycopene 20 mg·kg^-1 group (P<0.01). There was little change in ACE mRNA in model and lycopene groups. CONCLUSION Lycopene can decrease proteinuria, improve the renal function, reduce the renal pathological damage and up-regulate the expression of ACE2 mRNA and protein in diabetic model rats. The possible mechanism is that lycopene can block pathways of the local renin-angiotensin system in kidneys.