基于7.0 T心脏MR评估2型糖尿病小鼠早期心肌应变改变特点

Objective To investigate the characteristics of early myocardial mechanics changes in diabetic cardiomyopathy (DCM). Method Sixty healthy 4‑week‑old male C57BL/6J mice were randomly divided into the T2DM group (n=30) and the control group (n=30). The T2DM group was fed with high‑fat diet for 4 weeks, and accepted injection of a single high‑dose of streptozotocin (STZ) intraperitoneally. Finally, the model was established successfully in 23 mice. The control group was fed with a normal diet and treated with citrate buffer liquid at an equal dose as T2DM group. Then, nine mice were randomly selected from each of the two groups every 4 weeks until the end of the 24th week. Six of the nine mice were randomly selected to perform 7.0 T MR scanning after measuring blood glucose and body weight. Cine images were acquired through cardiovascular MR feature tracking (CMR‑FT). The obtained parameters included the left ventricle global peak circumferential strain (LV‑GPCS), left ventricle global peak radial strain(GPRS) and the ejection fraction (EF), etc. The rest three mice were sacrificed for observation of the changes of interstitial fibers and micro‑vessels in myocardial tissue with Sirius red staining. One‑way analysis of variance (ANOVA) and t test were used for comparison. Results There were significant differences in blood glucose levels between the two groups during the observation period (P<0.05). In the 4^th-24^th week, the value of GPCS in T2DM group showed a downward trend, and the difference was statistically significant (F = 8.23, P<0.001). Compared with the control group, the value of GPCS in T2DM group was statistically significant at the 20^th and 24^th week (the 20^th week: -11.4%±2.1% in the T2DM group vs. -14.3%±1.9% in the control group, t=2.54, P=0.029; the 24^th week: -12.3%±1.7% in the T2DM group vs. -14.6%±1.8% in the control group, t=2.35, P=0.040), while the EF value was different at the 24^th week (51%±5% in the T2DM group vs. 62%±6% in the control group, t=3.38, P= 0.007). There was no significant difference in the GPRS of the T2DM mice group over time or compared with the controls (P>0.05). Moreover, the pathological results showed that the myocardial interstitial fibers in the T2DM group had remarkably increased since the 12^th week. Conclusions The alterations in myocardial interstitial fibers and myocardial contractility appeared early in T2DM mice. Especially, the left ventricle global peak circumferential strain value is superior to the EF value in reflecting the early changes in DCM.