[Mechanism of reversion of myocardial interstitial fibrosis in diabetic cardiomyopathy by valsartan].

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)-1 and tumor growth factor (TGF)-beta(1) mRNA, expression, and Western blotting was used to detect the protein expression of TSP-1, active TGF-beta(1) (A-TGF-beta(1)) and latent TGF-beta(1) (L-TGF-beta(1)).

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/dt(max) 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/dt(max) 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/dt(max) 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-beta(1) 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-beta(1) 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-beta(1) and L-TGF-beta(1) 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-beta(1) 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-beta(1) between the valsartan group and DCM group.

CONCLUSION: Valsartan amelioorates myocardial interstitial fibrosis in DCM via TSP-1/TGF-beta(1) signaling pathway.