The disappearance of IPO in myocardium of diabetes mellitus rats is associated with the increase of succinate dehydrogenase-flavin protein

Abstract

Background: The aim of the present study was to investigate whether the disappearance of ischemic post-processing (IPO) in the myocardium of diabetes mellitus (DM) is associated with the increase of succinate dehydrogenase-flavin protein (SDHA).

Methods: A total of 50 Sprague Dawley rats, weighing 300-400 g, were divided into 5 groups according to the random number table method, each with 10 rats. After DM rats were fed a high-fat and -sugar diet for 4 weeks, they were injected with Streptozotocin to establish the diabetic rat model. Normal rats were fed the same regular diet for the same number of weeks. Next, the above rats were taken to establish a cardiopulmonary bypass (CPB) model. Intraperitoneal glucose tolerance test (IPGTT) and oral glucose tolerance test (OGTT) were used to detect whether the DM rat model was established successfully. Taking blood from the femoral artery to collect the blood-gas analysis indicators, and judged whether the CPB model is established. After perfusion was performed according to the experimental strategy, the area of myocardial infarction (MI), and serum creatine kinase isoenzyme (CK-MB) and cardiac troponin (CTnI) levels were measured. Finally, the relative mRNA and protein expression of SDHA was detected.

Results: The OGTT and IPGTT suggested that the DM rat model was successfully established. The arterial blood gas analysis indicated that the CPB model was successfully established. As compared with the N group, the heart function of the IR group was significantly reduced, the levels of myocardial enzyme markers, the area of MI, as well as the relative mRNA and protein expression of SDHA, were all increased. As compared with the IR group, the CK-MB and CTnI levels in the IPO group, the MI area, relative mRNA and protein expression of SDHA decreased. As compared with the IPO group, the myocardial enzyme content in the DM + IPO group, the MI area and the relative mRNA and protein expression of SDHA increased. As compared with the DM + IPO group, in the DM + IPO + dme group, the myocardial enzyme content, area of MI and relative mRNA and protein expression were all decreased.

Conclusion: IPO can inhibit the expression of SDHA, reduce MIRI and exert a cardioprotective effect in the normal rats. However, the protective effect of IPO disappears in the diabetic rats. The inhibitor dme combined with IPO can increase the expression of SDHA and restore the protective effect of IPO in DM myocardia.

Fig. 1

Grouping and perfusion strategy in rats. A total of 50 standard male Sprague–Dawley rats were randomly divided into 5 groups (n = 10, each group): The N, IR, IPO, DM + IPO and DM + IPO + dme groups. DM, diabetes mellitus; N, normal; IR, ischemia–reperfusion; IPO ischemia post-conditioning, DM + IPO DM ischemia post-conditioning, DM + IPO + dme DM ischemia post-conditioning with inhibitor

Fig. 2

Comparison of IPGTT and OGTT in each group of rats. a OGTT. b IPGTT. All data are expressed as the mean + SD. DM diabetes mellitus, N normal, IPGTT intraperitoneal glucose tolerance test, OGTT oral glucose tolerance test

Fig. 3

Changes in the heart function of rats from each group. a Changes of the MAP in rats in each group. b Changes in the HR in-vivo rats in each group. T0, 5 min before CPB; T1, at the beginning of CPB; T2, at cardiac arrest; T3, at the end of cardiac arrest; T4, after 5 min of reperfusion; T5, at the end of reperfusion. ^aP < 0.05 versus T0; ^bP < 0.05 versus. T4 in the N group; ^cP < 0.05 versus T5 in the N group. MAP mean arterial pressure, DM diabetes mellitus, HR heart rate, N normal, IR ischemia–reperfusion, IPO ischemia post-conditioning, DM + IPO DM ischemia post-conditioning; DM + IPO + dme DM ischemia post-conditioning with inhibitor

Fig. 4

Changes in the HCT of rats in each group. T0, 5 min before CPB; T1, at the beginning of CPB; T2, at cardiac arrest; T3, at the end of cardiac arrest; T4, after 5 min of reperfusion; T5, at the end of reperfusion. ^aP < 0.05 versus T0. HCT haematocrit, CPB cardiopulmonary bypass

Fig. 5

Comparison of isolated heart infarction area of rats in each group at the end of reperfusion. ^aP < 0.05 vs. the N group; ^bP < 0.05 versus the IR group; ^cP < 0.05 versus the IPO group; ^dP < 0.05 versus the DM + IPO group. N normal, IR ischemia–reperfusion, IPO ischemia post-conditioning, DM + IPO DM ischemia post-conditioning, DM + IPO + dme DM ischemia post-conditioning with inhibitor

Fig. 6

Changes in serum CK-MB and CTnI levels. a Changes in the serum CKMB content. b Changes in the serum CTnI content vs. the N group. ^aP < 0.05 versus the N group; ^bP < 0.05 versus the IR group; ^cP < 0.05 versus the IPO group; ^dP < 0.05 versus the DM + IPO group. CTnl cardiac troponin, CK-MB creatine kinase isoenzyme, N normal, IR ischemia–reperfusion, IPO ischemia post-conditioning, DM + IPO DM ischemia post-conditioning, DM + IPO + dme DM ischemia post-conditioning with inhibitor

Fig. 7

Ratio of target heart SDHA to internal reference gene GAPDH mRNA in each group. ^aP < 0.05 versus the N group; ^bP < 0.05 versus the IR group; ^cP < 0.05 versus the IPO group; ^dP < 0.05 versus the DM + IPO group. DM diabetes mellitus, SDHA dehydrogenase-flavin protein, N normal, IR ischemia–reperfusion, IPO ischemia post-conditioning, DM + IPO DM ischemia post-conditioning, DM + IPO + dme DM ischemia post-conditioning with inhibitor

Fig. 8

Western blotting was used to detect the protein expression of SDHA in the myocardium of each group. a Expression of SDHA and GAPDH proteins in the heart of rats in each group. b Ratio of SDHA to GAPDH of target protein of rat heart in each group. ^aP < 0.05 versus the N group; ^bP < 0.05 versus the IR group; ^cP < 0.05 versus the IPO group; ^dP < 0.05 versus the DM + IPO group. DM diabetes mellitus, SDHA dehydrogenase-flavin protein, N normal, IR ischemia–reperfusion, IPO ischemia post-conditioning, DM + IPO DM ischemia post-conditioning, DM + IPO + dme DM ischemia post-conditioning with inhibitor. Full-length gels are presented in Supplementary file