Cardiac function and fat composition in STZ-induced diabetic rats

(e) Figure 1. (a-d) Cardiac cine images of a rat heart at diastole (a. short axis and c. long axis) and systole (b. short axis and d. long axis). (e) The change in EF during the 16 week experiment period. (f-k) Cardiac Dixon short axis images at diastole of a rat heart before STZ injection (f. water & fat signals combined, g. water signal only, h. fat signal only); and 8 weeks after STZ injection (i. water & fat signals combined, j. water signal only, k. fat signal only). Discussion: A significant decrease in ejection fraction was detected using cine MRI in rats with STZ-induced diabetes at 8 weeks and 16 weeks. This is consistent with our previous studies on isolated perfused hearts of STZ rats, which showed that cardiac output was significantly attenuated (4). Histological studies in the same report also showed significant structural damage in LV of STZ rats. Diabetes in humans is always accompanied by LV hypertrophy and LV dysfunction under glycemia (5). Our results showed that STZ-diabetic rats can mimic the cardiac impairment observed in human disease. The observation suggests that STZ-injected rats can be used as an animal model for diabetic heart failure. Furthermore, diabetes caused a noticeable fat depletion in rat heart within 8 weeks. Fat depletion was always associated with heart failure (1). Fat composition in diabetic human heart has never been thoroughly investigated. The present study suggests that cardiac fat composition could be a useful biomarker for diabetic heart failure, and detecting fat content in heart using MRI could be a useful technique to determine this biomarker.