Diabetic cardiomyopathy attenuated the protective effect of ischaemic post-conditioning against ischaemia-reperfusion injury in the isolated rat heart model.

The present study was designed to investigate the efficacy of post-conditioning (POC) in the diabetic heart with myopathy (DCM) against ischaemia-reperfusion (I/R) injury in an isolated rat heart model. Present work includes three groups of male Wistar rat viz., (i) normal, (ii) diabetes mellitus (DM) and (iii) DCM and each group was subdivided into normal perfusion, I/R, and POC. Isolated heart from the rats was analysed for tissue injury, contractile function, mitochondrial function, and oxidative stress. Results demonstrated that unlike in DM heart and normal heart, POC procedure failed to recover the DCM heart from I/R induced cardiac dysfunction (measured via cardiac hemodynamics and infarct size. POC was unsuccessful in preserving mitochondrial subsarcolemmal fraction during I/R when compared with DM and normal heart. To conclude, the development of myopathy in diabetic heart abolished the cardioprotective efficacy of POC and the underlying pathology was linked with the mitochondrial dysfunction.KEY MESSAGESEarly studies reported contradicting response of diabetic heart towards post-conditioning mediated cardioprotection.Deteriorated mitochondrial function underlines the failure of post-conditioning in DCM.Efficacy of cardioprotection depends on the varying pathology of different diabetes stages.

Hydrogen sulfide postconditioning rendered cardioprotection against myocardial ischemia-reperfusion injury is compromised in rats with diabetic cardiomyopathy.

The present study aimed to investigate the efficacy of hydrogen sulfide (H2S) post-conditioning (HPOC) against ischemia-reperfusion (I/R) challenged diabetic rat hearts with or without cardiomyopathy using the Langendorff perfusion system. Male Wistar rats were randomly divided into different groups such as normal, diabetes mellitus (DM), and diabetic cardiomyopathy (DCM). Hearts from these groups were subjected to normal perfusion, I/R, and HPOC and were analyzed for cardiac physiology, cardiomyocyte injury, mitochondrial function, oxidative stress, and H2S metabolism. The results showed that HPOC protocol reduced the cardiac injury and improved the haemodynamics in normal and DM effectively, but not in DCM (RPP in mmHg*beats/min*103: HPOC- 32 ± 2, DM-HPOC-19 ± 1, DCM-HPOC-6 ± 2, LVDP in mmHg: HPOC- 96 ± 3, DM-HPOC-73 ± 2, DCM-HPOC-50 ± 3). DCM rats at the basal level exhibited perturbed myocardial architecture, mitochondrial dysfunction, and impaired glycolytic flux that failed to improve by HPOC treatment after I/R. HPOC exhibited a nominal improvement in the gene expression and activities of the H2S metabolizing enzymes such as cystathionine beta-synthase, rhodanese, and cystathionine-gamma-lyase in DCM hearts. Collectively, our results suggest that altered myocardial architecture along with exacerbated oxidative stress and mitochondrial dysfunction contribute towards the failure of HPOC cardioprotection against I/R-induced myocardial tissue injury in DCM.

Diabetic animal fed with high-fat diet prevents the protective effect of myocardial ischemic preconditioning effect in isolated rat heart perfusion model.

Diabetic heart (diabetes mellitus [DM]) has been shown to attenuate the beneficial effect of ischemic preconditioning (IPC) in rat heart. But the effect of IPC on diabetic rat heart that develops myopathy remains unclear. This study was designed to test the impact of IPC on diabetic cardiomyopathy (DCM) rat heart. Male Wistar rats were grouped as (a) normal, (b) DM (streptozotocin: 65 mg/kg; fed with normal diet), and (c) DCM (streptozotocin: 65 mg/kg; fed with high-fat diet). Isolated rat hearts from each group were randomly subjected to (a) normal perfusion, (b) ischemia-reperfusion (I/R), and (c) IPC procedure. At the end of the perfusion experiments, hearts were analyzed for injury, contractile function, mitochondrial activity, and oxidative stress. The results obtained from hemodynamics, cardiac injury markers, and caspase-3 activity showed that DCM rat displayed prominent I/R-associated cardiac abnormalities than DM rat heart. But the deteriorated physiological performance and cardiac injury were not recovered in both DM and DCM heart by IPC procedure. Unlike normal rat heart, IPC did not reverse mitochondrial dysfunction (determined by electron transport chain enzymes activity, ATP level, and membrane integrity, expression levels of genes like PGC-1ɑ, GSK3ß, complex I, II, and V) in DCM and DM rat heart. The present study demonstrated that IPC failed to protect I/R-challenged DCM rat heart, and the underlying pathology was associated with deteriorated mitochondrial function.

Mechanism of Hydrogen Sulfide Preconditioning-Associated Protection Against Ischemia-Reperfusion Injury Differs in Diabetic Heart That Develops Myopathy.

Hydrogen sulfide (H2S) is reported to be effective in the management of the myocardial ischemia-reperfusion (I/R) injury via PI3K/GSK3ß pathway in normal rats. However, its efficacy against I/R in the presence of diabetic cardiomyopathy is relatively obscure. Thus, the present work aimed to find out H2S-mediated cardioprotection against I/R in diabetic cardiomyopathy and to evaluate its mode of action using Langendorff isolated heart perfusion system. The present work includes three groups of rat, viz. (i) normal, (ii) diabetes mellitus (DM: streptozotocin: 35 mg/kg; normal diet), and (iii) diabetes + high-fat diet (DCM) (streptozotocin: 35 mg/kg; high-fat diet). The effect of NaHS (an H2S donor; 20 µM) on cardiac function in isolated rat hearts demonstrates that H2S preconditioning (HIPC) significantly attenuated myocardial injury in both DM and DCM hearts, as evidenced by the (i) improvement in hemodynamics, which includes rate pressure product [(in mmHg × 103 × bpm) DM: 40 to 56; DCM: 21 to 58] and left ventricular developed pressure [(in mmHg) DM: 53 to 74; DCM: 28 to 74), (ii) reduction in infarct size (25% to 8%) and attenuated caspase activity, compared to their respective I/R controls. Also, the observed positive recovery of mitochondrial function during HIPC treatment reinforces the cardioprotection by HIPC in DCM heart against I/R injury. However, HIPC could not repair I/R-induced oxidative stress in DCM rat heart. Further, to study the H2S mode of action, the experimental rats were exposed to a PI3K inhibitor (Wortmannin) and GSK3ß inhibitor (SB216763) before HIPC protocol, whose results suggest that unlike in normal and DM, HIPC mediates its cardioprotective effect independent of PI3K/GSK3ß pathway. To conclude, HIPC ameliorates I/R injury in DCM rat via an alternative pathway other than existing PI3K pathway, which is required to be probed under disease conditions.

Hydrogen sulfide preconditioning could ameliorate reperfusion associated injury in diabetic cardiomyopathy rat heart through preservation of mitochondria.

Evidence suggests that hydrogen sulfide precondition (HIPC) is an effective protocol in the management of ischemia reperfusion (I/R) by attenuating free radical and calcium overload in mitochondria. However the efficacy of HIPC is largely unknown in diabetic cardiomyopathy (DCM) hearts subjected to I/R procedure. Male Wistar rats were randomly divided into three groups: i) normal, ii) diabetes mellitus (DM), and iii) diabetic cardiomyopathy (DCM). DM and DCM animals were prepared by using streptozotocin injection at the age of 4 week (35 mg/kg, i.p). DCM animals were additionally administered with high fat diet for 3 months. Isolated rat hearts were perfused by using Langendorff apparatus with continuous hemodynamic monitoring. Following reperfusion, cardiac physiological efficiency was highly compromised in DCM heart (high infarct size by 94% and low relative pressure product by 65%) as compared to normal rat heart. HIPC effectively improved cardiac physiology of I/R challenged normal rat hearts by 62.5% (RPP), reduced injury by 60% (Infarct size) and subsequently preserved mitochondrial electron transport chain enzyme activities NQR by 57%, membrane potential, swelling behaviour, ATP content, ATP producing capacity and oxidative defence system by reducing lipid peroxidation by 55% compared with I/R. But in DM and DCM animals, isolated hearts conditioned with HIPC substantially improved cardiac physiology (RPP) by 44% in DM and 58% in DCM, arrest tissue injury (Infarct size) by 72% in DM and 79% in DCM and preserved mitochondrial activity only to its own sham control, primarily due to the basal level defect. Furthermore, we found that SSM fraction of diabetic heart mitochondria showed overall better improvement in their function than IFM by HIPC. However, mitochondrion experienced I/R associated oxidative stress was not improved by HIPC.

Streptozotocin-induced type II diabetic rat administered with nonobesogenic high-fat diet is highly susceptible to myocardial ischemia-reperfusion injury: An insight into the function of mitochondria.

RATIONALE: Our recent study suggested that ischemia-reperfusion (I/R) induced oxidative stress was minimal in the rat heart during initial stage of diabetes and the one that progressed to diabetic cardiomyopathy (DCM), despite having higher infarct and low cardiac performance. Mitochondrial dysfunction is an important mediator for adverse outcome in rat heart affected with diabetes, which is also a potential contributor for the cardiac reperfusion injury. OBJECTIVE: The current study aims to evaluate the susceptibility of diabetes heart with or without myopathy to I/R injury and its influence on cardiac mitochondrial function. METHODS AND RESULTS: Male Wistar rats (3 weeks old) were fed with high-fat diet for 8 weeks followed by diabetes mellitus (DM) induction via streptozotocin (35 mg/kg body weight) and maintained for further 4 weeks. The animal displayed cardiomyopathy characteristics like hypertrophy, fibrosis, and insulin resistance-termed diabetic cardiomyopathy (DCM). To study the specific effect of DCM on I/R, we included diabetic rats without cardiomyopathy. Induction of I/R in different groups suggested higher vulnerability to injury in DCM rat hearts than DM and normal (measured via hemodynamics, triphenyltetrazolium chloride stain, and apoptotic markers). Mitochondrial function at the subpopulation level was evaluated with respect to adenosine triphosphate (ATP) concentration, membrane potential, swelling behavior, and oxidative stress, wherein the results confirmed I/R-induced mitochondrial dysfunction. Unlike normal heart, DM, and DCM heart challenged to I/R exhibited altered ATP producing capacity among subsarcolemmal and interfibrillar mitochondria. CONCLUSION: The above results suggest that mitochondrial changes associated with diabetes and cardiomyopathy significantly contribute to the adverse outcome of I/R injury.

Evaluating the effect of green synthesised copper oxide nanoparticles on oxidative stress and mitochondrial function using murine model.

Green synthesis of metal nanoparticles (NPs) has now received the attention of researchers due to ease of preparation and its potential to overcome hazards of these chemicals for an eco-friendly milieu. In this study, copper oxide (CuO) NPs were synthesised via Desmodium gangeticum aqueous root extract and standard chemical method, further characterised by UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis and scanning electron microscopy. The nephrotoxicity of the NP obtained from two routes were compared and evaluated at subcellular level in Wistar rat, renal proximal epithelial cells (LLC PK1 cell lines) and isolated renal mitochondria. CuO NP synthesised by chemical route showed prominent nephrotoxicity measured via adverse cytotoxicity to LLC PK1 cells, elevated renal oxidative stress and damage to renal tissue (determined by impaired alanine transaminase, aspartate transaminase, urea, uric acid and creatinine in the blood). However, at the level of cell organelle, CuO NP from both routes are non-toxic to mitochondrial functional activity. The authors' finding suggests that CuO NP synthesised by chemical route may induce nephrotoxicity, but may be overcome by co-administration of antioxidants, as it is not mito-toxic.