糖尿病心肌病中转化生长因子β1相关的Smads信号通路的激活及缬沙坦的干预作用

目的探讨糖尿病心肌病（DCM）中转化生长因子β1（TGFβ1）相关的Smads信号通路的激活及缬沙坦的干预作用。方法雄性Wistar大鼠40只，随机分为3组：对照组（8只），DCM组（16只），缬沙坦组（16只），采用高脂高热量饲料喂养加小剂量链脲佐菌素（STZ）注射制作DCM大鼠模型。成模后缬沙坦组给以缬沙坦（30mg／kg）干预治疗，实验末观察大鼠生化指标的变化，血流动力学观察大鼠心功能的变化，应用电子显微镜、Masson染色、实时定量逆转录（RT）-PCR和Western印迹技术，检测各组大鼠左室心肌组织胶原含量，TGFβ1、TGFβⅡR、Smad2、Smad3及Smad7 mRNA和蛋白质表达水平的变化。结果DCM组大鼠心功能明显低于对照组（P〈0．01），左室心肌组织胶原含量明显高于对照组（17％±3％vs11％±3％，P〈0．01），存在心肌间质纤维化；同时TGFβ1、TGFβⅡR、Smad2和Smad3mRNA表达水平均高于对照组（0．0054±0．0009vs0．0126±0．0057，0．0523±0．0218vs0．0877±0．0272，0．0413±0．0186vs0．0884±0．0146，0．0064±0．0021vs0．012±0．0048，P〈0．05-0．01），Smad2／Smad7和Smad3／Smad7的mRNA的比值也明显高于对照组（P〈0．05），TGFβ1、磷酸化（P）-Smad2和P-Smad3蛋白质表达水平明显高于对照组（103±18vs143±17，107±21vs212±43，89±17vs151±32，P〈0．01），P-Smad2／Smad7和P-Smad3／Smad7蛋白质的比值也明显升高（P〈0．05）。应用缬沙坦干预治疗后，大鼠心功能明显好转，心肌间质胶原沉积减轻，同时上述分子异常均明显好转，Smad2、Smad3和Smad7之间的失平衡现象较DCM组减轻（均P〈0．05）。结论TGFβ1相关的Smads信号通路的激活及相关分子之间的平衡状态的改变可能是DCM心肌间质纤维化的机制之一，缬沙坦通过抑制这一信号途径，在一定程度上可逆转DCM心肌间质纤维化的发生和发展。

Activation of transforming growth factor-beta1/Smads signal pathway in diabetic cardiomyopathy and effects of valsartan thereon: experiment with rats

OBJECTIVE: To study the activation of transforming growth factor (TGF)-beta(1)/Smads signal pathway in diabetic cardiomyopathy (DCM) and effects of valsartan thereon. METHODS: 40 male Wistar rats were randomly divided into 3 groups: DCM group (n = 16, fed with high-calorie fat diet for 4 weeks, injected intraperitoneally with streptozocin so as to establish DCM model, and then perfused into the stomach with normal saline once daily since the injection of STZ for 16 weeks), valsartan group (n = 16, perfused into the stomach with valsartan at the dose of 30 mg/kg once a day for 16 weeks after the establishment of DCM model), and control group (n = 8, fed with normal diet and perfused into the stomach with normal saline once daily for 16 weeks). At the end of the experiment, the contents of fast blood-glucose (FBG), fast insulin (FIN), serum cholesterol, and triglyceride were detected, and insulin sensitivity index (ISI) was calculated. Cardiac catheterization was performed to measure the hemodynamics indexes: left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), and maximal rise/fall velocity of ventricular pressure (+/- dp/dt(max)), and the left ventricular diastolic function (T) was calculated. Pieces of myocardium tissue were taken out to undergo ultrastructural histopathological examination by transmission electron microscopy. The content of collagen was quantified by Masson three-color staining. Real-time RT-PCR and Western-blotting were used to detect the mRNA expression and protein expression of TGFbeta(1), TGFbetaRII, Smad2, Smad3, and Smad7. RESULTS: By the end of experiment the levels of FBG, triglyceride, and cholesterol increased and the ISI decreased significantly in the DCM and valsartan groups (all P < 0.01). Compared with the valsartan and control groups the levels of LVEDP and T significantly increased, and the levels of LVSP and +/- dp/dt(max), significantly decreased (all P < 0.01); and the LVEDP of the valsartan group was significantly higher than that of the control group and the +/- dp/dt(max) of the valsartan group was significantly lower than that of the control group (P < 0.01). The volume of collagen in the myocardial tissue of the DCM group was 17% +/- 3%, significantly higher than that of the control group (11% +/- 3%, P < 0.01). The content of collagen in the myocardial tissue of the valsartan group was lower significantly than that of the DCM group. The levels of mRNA expression of TGFbeta(1), TGFbetaRII, Smad2, and Smad3 were 0.0126 +/- 0.0057, 0.0877 +/- 0.0272, 0.0884 +/- 0.0146, and 0.012 +/- 0.0048 respectively, all significantly higher than those of the control group (0.0054 +/- 0.0009, 0.0523 +/- 0.0218, 0.0413 +/- 0.0186, and 0.0064 +/- 0.0021 respectively, all P < 0.05 - 0.01). The ratios Smad2/Smad7 and Smad3/Smad7 of the DCM group were significantly higher than those of the control group (both P < 0.05). The protein levels of TGFbeta(1), P-Smad2, and P-Smad3 were 143 +/- 17, 212 +/- 43, and 151 +/- 32 respectively, all significantly higher than those of the control group (103 +/- 18, 107 +/- 21, and 89 +/- 17 respectively, P < 0.01). The P-Smad2/Smad7 and P-Smad3/Smad7 of the DCM group were significantly higher than those of the control group (both P < 0.05), The Smad2/Smad7 (or P-Smad2/Smads7) and Smad3/Smad7 (or P-Smad3/Smads7) of the valsartan group was significantly lower than those of the DCM group (both P < 0.05). CONCLUSION: Activation of TGFbeta(1)/Smads signal pathway and imbalance between Smad2, 3 and Sma7 may be one of the mechanisms of myocardial interstitial fibrosis in DCM. Valsartan can prevent myocardium from damage by blocking the signal pathway.