The Expression Of Neuregulin-1in Myocardial Tissue Of Diabetic Rats

Objective:To investigate the expression of neuregulin-1(NRG-1) mRNA and protein level in the cardiac tissue of diabetic rats and explore the role of NRG-1in cardiomyopathy.Methods:45Male SD rats were randomly divided into4,8and12weeks diabetic group(A1, A2and A3group, n=10, each group)and4,8,12weeks control group(B1, B2and B3group, n=5, each group). Diabetic rat model was induced by a single intraperitoneal injection of streptozotocin (STZ,55mg/kg). The pathological and histological changes of the cardiac tissue of diabetic rats were observed by HE and Masson staining. Immunohistochemistry methods were used to observe the express parts of NRG-1in cardiac tissue of rats. Left ventricular mass index (LVMI), echocardiographic parameters, collagen volume fraction (CVF) and the expression level of NRG-1mRNA and protein were observed at4weeks,8weeks and12weeks respectively after STZ injection.Results:There were no statistical significant differences in LVMI,CVF echocardiographic parameters and the expression level of NRG-1mRNA and protein between A1and B1groups (each P>0.05); LVMI, CVF and left ventricular systolic dimension (LVESD) in A2and A3group were much higher than those in the same point time groups[①A2group vs B2group:(27.03±2.48)%vs (15.37±1.72)%,(3.49±0.41) mm vs (3.02±0.27) mm,(10.23±3.69)%vs (1.87±0.37)%, each P<0.05;②A3group vs B3group:(32.53±3.41)%vs (17.07±2.18)%,(3.79±0.39) mm vs(3.01±0.32)mm,(17.29±4.67)%vs (1.99±0.41)%, each P<0.01]; Compared with B2group, left ventricular fractional shortening(LVFS), left ventricular ejection fraction(LVEF) in A2group decreased but had no statistical significances[(48.3±5.50)%vs (51.4±4.23)%,(82.5±3.24)%vs(84.3±2.46)%, eachP>0.05); LVFS,LVEF and the expression level of NRG-1mRNA and protein in A3group many lower than those in B3group [(40.1±3.91)%vs (53.3±5.37)%,(71.5±4.53)%vs (83.6±2.97)%,(0.018±0.005) vs (0.045±0.008),(0.171±0.054) vs (0.324±0.039), each P<0.01]; Correlation analysis indicated that CVF positively correlated with LVMI (r=0.915, P<0.01), while negatively correlated with LVFS and LVEF (r1=-0.903, P<0.01; r2=-0.872, P<0.05).Conclusions:①Changes of cardiac structure and function have occurred in the early stages of diabetes induces by STZ, and the injury of heart become more and more severe with the progression of diabetes:myocardium mesenchyme fibrosis, cardiac remodeling and cardiac function decreased significantly, which consistent with the character of diabetic cardiomyopathy.②The expression level of NRG-1mRNA and protein in the cardiac tissue of diabetic rat are down-regulated at12weeks after STZ injection, which may take some roles in the progression of diabetic cardiomyopathy.