Effects of hyperglycemia on remodeling of acute myocardial infarction in rats

Abstract

Acute myocardial infarction (MI) remodeling consequences for cardiac function were investigated in diabetes (hyperglycemia) induced by streptozotocin (STZ) in rats. The measurements were performed after 15 days of STZ induction (50 mg/kg iv) and/or 48hs of MI. The following parameters were evaluated: levels of FFA, TG (in plasma and the left ventricle–LV) and glycogen in the LV, the cardiac remodeling, the autonomic nervous system activity, and the oxidative stress in the LV. The Wistar rats (n=8 per group) were divided into 4 groups: control (C); control infarcted (CI); diabetic (D); diabetic infarcted (DI). After 15 days of STZ, the MI was induced by left coronary artery occlusion (□ 25% MI area between the CI and DI groups). The CI group had increased: end‐posterior wall thickness (LVPW), interventricular septum thickness the relative wall thickness and reduced LV cavity, as consequence of cardiac remodeling and increased LV mass. The D group had reduced LVPW (0.11 ± 0.001 cm) as compared with the C (0.13 ± 0.003 cm). DI group had increased LVPW (0.14 ± 0.005 cm). The systolic function was not different between groups. However, the D and CI group exhibited increased isovolumetric relaxation time (IVRT ms): D: 34 ± 1; CI: 30 ± 2.4 vs C: 23 ± 0.7 and The E‐wave desaceleration (ms) was increased in D: 50 ± 0.9 vs C: 40 ± 0.6, having diastolic dysfunction in diabetic rats but there was no impairment in MI (DI: 35 ± 2.3). The variance of heart rate (HRV m2) was reduced by diabetes (D: 18 ± 2.5; DI: 25 ± 3) vs the C group (81 ± 3), as well as the low (LF) and high (HF) frequency bands (sympathetic and vagal components). The MI increased in non‐diabetic rats the HRV (CI: 99 ± 14) and the LF (m2) (CI: 1.8 ± 0.5 vs D: 0.6 ± 0.1; DI: 1 ± 0.2). The variance of blood pressure (mmHg) was reduced by diabetes (D: 8.6 ± 0.7; DI: 5.3 ± 0.6) as compared to C (24 ± 3) and CI (18 ± 3) and the LF were increased only in the CI group (2.7 ± 0.17) vs DI group (1 ± 0.2). The MI increased in non‐diabetic rats the lipid peroxidation (1156 ± 125) vs C: 645 ± 111; D: 945 ± 117; DI: 894 ± 112) and both the MI groups increased the anion superoxide, however, only DI had increased antioxidant enzyme activities (catalase, glutathione peroxidase, superoxide dismutase) improving the redox balance after MI. DI group had reduced TG (1.4 ± 0.19) and glycogen (43 ± 7) content in the LV that was increased before the MI (D: 5.4 ± 0.9 vs C: 1.1 ± 0.2; D: 316 ± 79 vs C: 20 ± 5, respectively mg/g of LV). Therefore, the hyperglycemia previous to ischemia promoted a more efficient metabolic response on remodeling and cardiac function with improved oxidative balance.Support or Funding InformationFAPESP, CNPq, and CAPES supported this research.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.