Effects of insulin treatment on collagen remodeling after myocardial infarction in rats

AIM: To investigate whether insulin treatment attenuates collagen remodeling of non-infarcted myocardium after myocardial infarction(MI) in rats.METHODS: MI models were produced by ligation of the anterior descending coronary artery.Thirty four adult male rats were randomized to receive one of the following treatments: sham(n=6),saline [4 ml/(kg·h) i.v.injection beginning 20 min before ischemia and continuing for 2 h;n=14] and insulin treatment(50 U/L,i.v.injection following the same routine and hypodermic injection of insulin [0.5 U/ml,1 ml/(kg·day)] for 7 days after ischemia surgery;n=14).Parameters of echocardiogram were compared prior to and 1 and 4 weeks after operation.Hydroxyproline concentration was detected using immunochemistry.Collagen I and collagen Ⅲ expressions were measured by Western blot.RESULTS: Insulin treatment significantly improved cardiac function as evidenced by increased left ventricular ejection fraction(LVEF) at 1 and 4 weeks after MI(P0.05,P0.01).Cardiac remodeling decreased post-MI as evidenced by reduced collagen content(P0.05).Western blot showed that the ratios of myocardial collagen Ⅰ/Ⅲ of rats 1 and 4 weeks after MI were significantly higher than those in the sham group(P0.05).Insulin treatment reduced the ratios of collagen Ⅰ/Ⅲ compared with those in saline hearts 1 week post-MI(P0.05),whereas there were no differences in the ratios of collagen Ⅰ/Ⅲ 4 weeks post-MI.CONCLUSION: Insulin prevents heart remodeling in non-infarcted myocardium after MI by decreasing cardiac collagen Ⅰ/Ⅲ ratio.