Effect of metabolic disorders of branched chain amino acids on myocardial ischemia/reperfusion injury in type 2 diabetic mice

  AIM  To investigate the effect of metabolic disorders of branched chain amino acids (BCAA) on myocardial ischemia/reperfusion (MI/R) injury in type 2 diabetic mice.

  METHODS  T2DM was induced by a high-fat diet (HD) plus low-dose streptozotocin (STZ) intraperitoneal injection. Sixty male C57BL/6 mice were randomly divided into six groups: normal control group (Control); T2DM group (T2DM); T2DM + saline treatment group (T2DM + Vehicle); (T2DM + BT2) treatment group T2DM + specific branched-chain α-ketoacid dehydrogenase kinase (BDK) inhibitor, 3,6-dichlorobenzothiophene-2-carboxylic acid (BT2); T2DM + saline treatment + I/R group (T2DM + Vehicle I/R) and T2DM+BT2 treatment + I/R group (T2DM + BT2 + I/R). H9C2 cells were cultured in vitro and randomly divided into three groups: control group (Control), hypoxia/reoxygenation group (H/R) and H/R + BT2 treatment group (H/R + BT2). The cells were incubated with different concentrations of BCAA or BCKA. ELISA method was used to determine the levels of BCAA and BCKA and myocardial BCKD enzyme activity in plasma, myocardial tissue and cultured supernatants and Western blot was used to determine the levels of BCKDE1α and p-BCKDE1α. The cell viability was assayed using CCK-8 method. Echocardiography was used to determine left ventricular ejection fractions and TTC/Evans blue staining was used to determine myocardial infarct size.

  RESULTS  The T2DM mouse model was successfully established by high-fat diet (HD) plus low-dose streptozotocin (STZ) intraperitoneal injection, the level of insulin in T2DM group was significantly higher than that in Control group(P < 0.01). BCAA metabolic disorder was found in myocardium of T2DM mice, BCAA and BCKA levels in plasma and myocardium of T2DM mice were significantly increased (P < 0.01), BCKD enzyme activity in myocardium of T2DM mice was significantly decreased (P < 0.01), p-BCKDE1α/BCKDE1α was significantly increased (P < 0.01). After the treatment of BT2 in T2DM mice, the BCAA metabolic disorder was significantly improved and the area of MI of the T2DM mice was decreased (P < 0.01). H/R injury in H9C2 cells was increased with exogenous BCKA incubation in high concentration and BT2 treatment alleviated this injury(P < 0.05).

  CONCLUSION  BCAA metabolic disorder is one of the possible causes of increased MI/R injury in diabetes and BT2 may be an effective drug used to correct T2DM BCAA metabolic disorders.