缬沙坦逆转糖尿病心肌病大鼠心肌间质纤维化的作用

Mechanism of reversion of myocardial interstitial fibrosis in diabetic cardiomyopathy by valsartan

目的探讨缬沙坦逆转糖尿病心肌病(DCM)心肌间质纤维化的作用机制。方法雄性Wistar大鼠40只随机分为3组对照组(8只),DCM组(16只),缬沙坦干预组(16只)。采用高脂高热量饮食诱导出胰岛素抵抗,加小剂量链脲佐菌素(STZ)注射建立DCM动物模型。利用Masson染色、实时定量逆转录-聚合酶链反应、Western印迹技术,检测左室心肌胶原含量、血小板反应素-1(TSP-1)、TGFβ1mRNA表达水平和蛋白质表达的变化。结果与对照组相比,DCM大鼠左室心肌组织胶原含量明显升高(11%±3%vs17%±3%,P<0·01),存在心肌间质纤维化;TSP-1mRNA和蛋白质表达水平均明显升高(0·0089±0·0034vs0·0141±0·0037,96±17vs130±17,均P<0·05),TGFβ1mRNA、活性和非活性TGFβ1蛋白质表达水平亦明显升高(0·0054±0·0009vs0·0126±0·0057,103±18vs143±17,99±20vs155±35,均P<0·01);应用缬沙坦进行干预治疗后,除非活性TGFβ1蛋白质表达水平无明显变化外,上述异常均明显减轻。结论缬沙坦通过抑制TSP-1/TGFβ1信号传导途径在逆转DCM心肌间质纤维化发生发展过程中起着重要的作用。

Objective To investigate the mechanism of reversion of myocardial interstitial fibrosis in diabetic cardiomyopathy （DCM） by valsartan. Methods Forty male wistar rats were randomly divided into 3 groups： DCM group, n = 16, fed with high-fat diet for 4 weeks and injected intraperitoneally with streptozocin （STZ） once to induce hyperglycemia so as to construct a DCM model, and then perfused into the stomach with normal saline; valsartan group, n = 16, to be constructed into DCM model and then perfused into the stomach with valsartan once daily ; and control group （ n = 8, fed with normal food and perfused into the stomach with normal saline. Four weeks after feeding （i. e. , before injection of STZ）, 1 week after STZ injection, and by the end of experiment after 12-hour fasting samples of venous blood were collected to detect the contents of triglyceride and fasting blood-glucose and insulin ; by the end of experiment miniature cardiac catheter was inserted into the left ventricle to conduct hemodynamic examination. Then myocardium tissues were collected, collagen content was detected by Masson staining, real-time RT-PCR was used to detect the mRNA expression of thrombospondin （TSP）-I and tumor growth factor （TGF）-β1 mRNA, expression, and Western blotting was used to detect the protein expression of TSP-1, active TGF-β1 （A- TGF-β1 ） and latent TGF-β1 （ L- TGF-β1 ）. Results By the end of the experiment, the body weights, and insulin sensitivity index were significantly lower and fasting blood-glucose, and serum triglyceride and cholesterol were significantly higher in the DCM group and valsartan group in comparison with those in the control group （all P 〈 0.01 ）, however, there was no significant differences in fasting insulin among these 3 groups. The values of left ventricular systolic pressure （LVSP） and ± dp/dtmax, were significantly lower and left ventricular end diastolic pressure were significantly higher in the DCM group in comparison with the control group （ all P 〈 0. 01 ）. The LVSP and -dp/dtmax were significantly higher and LVEDP was significantly lower in the valsartan group than in the DCM group （ all P 〈 0. 05 ）. The LVEDP was significantly higher and -dp/dtmax was significantly lower in the valsartan group than in the control group. Electron microscopy showed the distribution of a great amount of collagen in the myocardial interstitial tissue. The collagen content of the DCM group was 17 ± 3, significantly higher than that of the control group （ 11 ± 3, P 〈 0.05 ）, and the collagen content of the valsartan group was 13 ±3, significantly lower than that of the DCM group （P 〈0.05）. The mRNA expression of TSP-1 and that of TGF-β1 were significant higher in the DCM group than in the control group （ both P 〈 0.05 ）, and were significantly lower in the valsartan group than in the DCM group （ both P 〈 0.05 ） ; however, the TGF-β1 mRNA expression in the valsartan group was significantly higher in the valsartan group than in the control group （ P 〈 0.05 ）. The values of protein expression of TSP-1, A- TGF-β1 and L- TGF-β1 were all significantly higher in the DCM group than in the control group （ all P 〈 0.05 ）, and the values of protein expression of TSP-1 and A- TGF-β1 in the valsartan group were both significantly lower than those in the DCM group （ both P 〈 0.05 ）, however, there was no significant difference in the protein expression of L- TGF-β1 between the valsartan group and DCM group. Conclusion Valsartan amelioorates myocardial interstitial fibrosis in DCM via TSP-1/ TGF-β1 signaling pathway.