2004 Volume 50 Issue 4 Pages 356-365
Diabetic animal models are used extensively to dissect the mechanisms underlying diabetic cardiomyopathy. For such studies, detection of cardiac dysfunction is critical, and therefore, the present study comparatively examined cardiac function in mice 100 days after strepotozotocin (STZ)-induced diabetes using three complementary techniques: electrocardiography (ECG), echocardiography and left ventricular (LV) hemodynamic analysis. Histological changes were also assessed by periodic acid-Schiff (PAS)-positive materials and Masson's trichrome staining and immunohistochemical staining for type IV collagen. ECG monitoring for 2 hr in diabetic and control mice revealed no abnormality. By echocardiography, diabetic mice showed significant decreases in LV chamber diameter at end-diastole and end-systole but no other abnormalities, as compared to control mice. Hemodynamic evaluation in diabetic mice revealed that although basal parameters of cardiac function were similar to control, β-adrenergic responsiveness was significantly reduced in diabetic mice, indicating a loss of inotropic reserve and early myocardial dysfunction. Histological staining showed mild but significant increases in interstitial fibrosis in diabetic mice, confirming early diabetic cardiomyopathy. These results indicate that despite examination by ECG and resting hemodynamic may not sensitive approaches to reveal early diabetic cardiomyopathy, resting echocardiography and stressing hemodynamic analysis by evaluation of contractile provocation and inotropic reserve are able to uncover the evidence of early subtle mechanical dysfunction.