Abstract 3366: Thrombin Fragment (TP508) Protects Myocardium in the Setting of Acute Ischemia-reperfusion Injury in Diabetic Pigs
OBJECTIVE: Myocardial ischemia-reperfusion injury (IR) occurs frequently in the setting of hyperglycemia. We investigated the potential efficacy of a novel thrombin fragment (TP508) on IR injury in a porcine type I diabetic model.
METHODS: Sixteen alloxan-induced diabetic male Yucatan pigs underwent 60 min of mid-left anterior descending (LAD) coronary artery occlusion followed by 120 min of reperfusion. Pigs received either placebo (DM control, n=8), or TP508 (DM TP508, n=8, as bolus of 1 mg/kg 50 min into ischemia followed by an infusion of 2.5 mg/kg/hr at the onset of reperfusion). Additionally, eight pigs were used as non-diabetic controls (ND). Myocardial function was monitored throughout the experiment. The area at risk and myocardial necrosis were determined TTC staining. Protein expression was assessed by immunoblot. Coronary microvascular relaxation was measured.
RESULTS: Myocardial necrosis was lower in both diabetic groups vs. ND control group, and TP508-treatment further lowered myocardial necrosis by 75% vs. DM control group (p=0.04). Indices of global left ventricular (LV) function were lower in both diabetic groups vs. ND control (p<0.05), whereas regional function in the ischemic area was better in both diabetic groups (p=0.05). Endothelium-dependent coronary microvascular relaxation was greater in the TP508-treated group vs.DM and ND control groups (p=0.05), and was associated with greater expression of phospho-eNOS(Ser1177) (p=0.05). The expression of mTOR and phospho-p38 were higher, whereas the ratio of LC3B II/I was lower in the TP508-treated group vs. control groups (p=0.05). The expression phospho-PDK1(Ser241) and phospho-4E-BP1were higher in both diabetic groups vs. ND control group (p<0.05). The expression of GSK-3beta was higher in the DM control group vs. DM TP508 and ND control groups, whereas the expression of phospho-GSK-3beta(Ser9) was lower in both DM groups vs. ND control group (p<0.05). The expression of phospho-Akt(Thr308) trended to be higher in both DM groups vs. ND control (p=0.09).
CONCLUSIONS: This study demonstrates that TP508 may offer cardioprotection via attenuation of autophagy and induction of cell survival signaling following IR injury in the setting of diabetes and hyperglycemia.