Ischemic conditioning: the challenge of protecting the diabetic heart

A double-edged sword of immuno-microenvironment in cardiac homeostasis and injury repair

The response of immune cells in cardiac injury is divided into three continuous phases: inflammation, proliferation and maturation. The kinetics of the inflammatory and proliferation phases directly influence the tissue repair. In cardiac homeostasis, cardiac tissue resident macrophages (cTMs) phagocytose bacteria and apoptotic cells. Meanwhile, NK cells prevent the maturation and transport of inflammatory cells. After cardiac injury, cTMs phagocytose the dead cardiomyocytes (CMs), regulate the proliferation and angiogenesis of cardiac progenitor cells. NK cells prevent the cardiac fibrosis, and promote vascularization and angiogenesis. Type 1 macrophages trigger the cardioprotective responses and promote tissue fibrosis in the early stage. Reversely, type 2 macrophages promote cardiac remodeling and angiogenesis in the late stage. Circulating macrophages and neutrophils firstly lead to chronic inflammation by secreting proinflammatory cytokines, and then release anti-inflammatory cytokines and growth factors, which regulate cardiac remodeling. In this process, dendritic cells (DCs) mediate the regulation of monocyte and macrophage recruitment. Recruited eosinophils and Mast cells (MCs) release some mediators which contribute to coronary vasoconstriction, leukocyte recruitment, formation of new blood vessels, scar formation. In adaptive immunity, effector T cells, especially Th17 cells, lead to the pathogenesis of cardiac fibrosis, including the distal fibrosis and scar formation. CMs protectors, Treg cells, inhibit reduce the inflammatory response, then directly trigger the regeneration of local progenitor cell via IL-10. B cells reduce myocardial injury by preserving cardiac function during the resolution of inflammation.

Remote liver ischemic preconditioning attenuates myocardial ischemia/reperfusion injury in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) exhibits a higher sensitivity to myocardial ischemia/reperfusion (I/R) injury and may compromise the effectiveness of cardioprotective interventions, including ischemic preconditioning. We previously found that liver ischemic preconditioning (RLIPC) could limit infarct size post I/R in non-diabetic rat hearts and further exerted anti-arrhythmic effects in diabetic or non-diabetic rats after myocardial I/R, however, little is known regarding the effect of RLIPC on infarct-sparing in diabetic hearts. In this study, we evaluated the protective effects of RLIPC on I/R injury in streptozotocin-induced type 1 diabetic rats. Type 1 diabetes mellitus was induced by one-time intraperitoneal injection of streptozotocin in Sprague-Dawley rats. Rats were exposed to 45 min of left anterior descend in (LAD) coronary artery occlusion, followed by 3 h of reperfusion. For liver ischemic preconditioning, four cycles of 5 min of liver I/R stimuli were performed before LAD occlusion. The cardioprotective effect of RLIPC was determined in diabetic rats. Compared to non-RLIPC treated DM rats, RLIPC treatment significantly reduced infarct size and cardiac tissue damage, inhibited apoptosis in diabetic hearts post I/R. RLIPC also improved cardiac functions including LVESP, LVEDP, dp/dtmax, and - dp/dtmax. In addition, RLIPC preserved cardiac morphology by reducing the pathological score post I/R in diabetic hearts. Finally, Westernblotting showed that RLIPC stimulated phosphorylation of ventricular GSK-3β and STAT-5, which are key components of RISK and SAFE signaling pathways. Our study showed that liver ischemic preconditioning retains strong cardioprotective properties in diabetic hearts against myocardial I/R injury via GSK-3β/STAT5 signaling pathway.

Comparison of infarction size, complete ST-segment resolution incidence, mortality and re-infarction and target vessel revascularization between remote ischemic conditioning and ischemic postconditioning in ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention

Introduction

Due to higher morbidity and mortality, ST-segment elevation myocardial infarction (STEMI) causes many public health problems.

Aim

To observe effects of remote ischemic conditioning (RIC) and ischemic postconditioning (IPC) on patients diagnosed as STEMI undergoing primary percutaneous coronary intervention (pPCI).

Material and methods

This meta-analysis was conducted using indirect comparison by conducting a network meta-analysis (NMA). We conducted searches by utilizing PubMed and the other databases to identify randomized controlled trials (RCTs) that described IPC or RIC treated patients diagnosed with STEMI during processes of pPCI. Enzymatic infarct size and infarction size were evaluated and cardiac events were assessed during the follow-up.

Results

Pooled results showed that lower enzymatic infarction size was associated with the RIC group compared to the IPC group (IPC vs. RIC: standardized mean difference (SMD) = 1.126; 95% confidence interval (CI): 0.756–1.677). Compared with IPC, RIC significantly reduced infarction size, which was assessed using cardiac magnetic resonance (CMR) (SMD = 1.113; 95% CI: 0.674–1.837). We noted a potential toward greater complete ST-segment resolution in RIC patients compared with IPC patients (odds ratio (OR) = 0.821; 95% CI: 0.166–4.051). No significant difference existed in all-cause mortality (OR = 2.211; 95% CI: 0.845–5.784), Target vessel revascularization (TVR) (OR = 0.045; 95% CI: 0.001–.662) or re-infarction (OR = 1.763; 95% CI: 0.741–4.193).

Conclusions

This meta-analysis suggested RIC was correlated with significantly smaller infarction size compared to IPC. No significant superiority between RIC and IPC has been observed in this study on cSTR incidence, mortality and re-infarction or TVR.

Up-regulation of PERK/Nrf2/HO-1 axis protects myocardial tissues of mice from damage triggered by ischemia-reperfusion through ameliorating endoplasmic reticulum stress

Background

Ischemia-reperfusion (I/R) injury, which leads to additionally cardiac tissue damage, is a severe adverse effect of reperfusion therapeutics used for the treatment of acute myocardial infarction. Agents capable of alleviating I/R-induced myocardial injury are urgently needed. In this study, we investigated whether up-regulation of PERK/Nrf2/HO-1 axis provided protective roles for murine myocardium suffering I/R intervention.

Methods

The in vivo I/R model was formed by ligation of the left anterior descending (LAD) coronary artery of C57BL/6J mice. All animals were assigned into the following groups at random: sham, I/R, rAAV9-PERK + I/R, rAAV9-Nrf2 + I/R, rAAV9-HO-1 + I/R, siRNA-HO-1 + rAAV9-PERK + I/R. The ligation of LAD was released after 30 min of ischemia, which was followed by reperfusion of LAD for 4 h. Then the cardiac tissues and blood serum were collected. TUNEL staining, ELISA assay, TTC staining, Western blotting and real-time PCR were used to determine I/R injury-related indicators.

Results

Our results showed that I/R administration triggered cardiomyocytes apoptosis and LDH and CK-MB release, yet overexpression of PERK decreased cellular apoptosis index in the cardiac tissue and reduced levels of LDH and CK-MB in the serum. We further found that the protective actions of PERK against I/R-evoked cardiac damage might be attributed to up-regulation of Nrf2/HO-1 signaling transduction, given that overexpression of Nrf2 and HO-1 ameliorated cardiac cell apoptosis and reduced the size of infarction and ischemia in the myocardial tissue, yet gene silencing of HO-1 invalidated the beneficial roles of PERK overexpression in improving I/R-induced cardiac injury. Then, we investigated whether PERK-activated Nrf2/HO-1 cascade affected endoplasmic reticulum stress (ERS), considering the crucial roles of ERS-associated apoptosis in the development of I/R damage. Our findings indicated that up-regulation of PERK-mediated Nrf2/HO-1 pathway induced the expression reduction of GRP78, CRT, CHOP and caspase-12 both at the transcriptional and translational level.

Conclusions

We, for the first time, discovered that up-regulation of PERK/Nrf2/HO-1 axis improved I/R-induced myocardial injury via reducing ERS-related signal molecules and downstream pro-apoptotic factors.

Hyperglycemia-Induced Oxidative Stress Abrogates Remifentanil Preconditioning-Mediated Cardioprotection in Diabetic Rats by Impairing Caveolin-3-Modulated PI3K/Akt and JAK2/STAT3 Signaling

Diabetic hearts are more vulnerable to ischemia/reperfusion (I/R) injury and less responsive to remifentanil preconditioning (RPC), but the underlying mechanisms are incompletely understood. Caveolin-3 (Cav-3), the dominant isoform of cardiomyocyte caveolae, is reduced in diabetic hearts in which oxidative stress is increased. This study determined whether the compromised RPC in diabetes was an independent manifestation of hyperglycemia-induced oxidative stress or linked to impaired Cav-3 expression with associated signaling abnormality. RPC significantly attenuated postischemic infarction, cardiac dysfunction, myocardial apoptosis, and 15-F2t-isoprostane production (a specific marker of oxidative stress), accompanied with increased Cav-3 expression and enhanced Akt and STAT3 activation in control but not in diabetic rats. Pretreatment with the antioxidant N-acetylcysteine (NAC) attenuated hyperglycemia-induced reduction of Cav-3 expression and Akt and STAT3 activation and restored RPC-mediated cardioprotection in diabetes, which was abolished by cardiac-specific knockdown of Cav-3 by AAV9-shRNA-Cav-3, PI3K/Akt inhibitor wortmannin, or JAK2/STAT3 inhibitor AG490, respectively. Similarly, NAC could restore RPC protection from high glucose and hypoxia/reoxygenation-induced injury evidenced by decreased levels of LDH release, 15-F2t-isoprostane, O₂ ^-, and JC-1 monomeric cells, which were reversed by caveolae disrupter methyl-β-cyclodextrin, wortmannin, or AG490 in isolated primary cardiomyocytes or siRNAs of Cav-3, Akt, or STAT3 in H9C2 cells. Either methyl-β-cyclodextrin or Cav-3 knockdown reduced Akt and STAT3 activation. Further, the inhibition of Akt activation by a selective inhibitor or siRNA reduced STAT3 activation and vice versa, but they had no effects on Cav-3 expression. Thus, hyperglycemia-induced oxidative stress abrogates RPC cardioprotection by impairing Cav-3-modulated PI3K/Akt and JAK2/STAT3 signaling. Antioxidant treatment with NAC could restore RPC-induced cardioprotection in diabetes by improving Cav-3-dependent Akt and STAT3 activation and by facilitating the cross talk between PI3K/Akt and JAK2/STAT3 signaling pathways.

Reduced baseline diameter and contraction of peripheral retinal arterioles immediately after remote ischemia in diabetic patients

PURPOSE

Remote ischemic conditioning (RIC) implies that transient ischemia in one organ can affect blood flow and protect from ischemia in another remote organ such as the retina. The purpose of the present study was to investigate the effect of RIC on the diameter of retinal arterioles in patients with diabetic retinopathy and whether this effect differs among peripheral and macular vessels.

METHODS

In twenty type 1 diabetes patients aged 20-31 years, the Dynamic Vessel Analyzer (DVA) was used to measure diameters of peripheral and macular arterioles during rest, isometric exercise, and flicker stimulation. Measurements were obtained before, immediately after, and 1 h after RIC, and were compared to responses obtained from normal persons.

RESULTS

The reduced baseline diameter (p < 0.009) and contraction of peripheral retinal arterioles during isometric exercise (p = 0.025) observed immediately after RIC in normal persons were absent in the studied diabetic patients.

CONCLUSIONS

RIC affects the diameter of peripheral but not macular arterioles in normal persons, but the response is abolished in diabetic patients.

TRIAL REGISTRATION

NCT03906383.

Peripheral Mechanisms of Remote Ischemic Conditioning

Ischemic conditioning induces an endogenous protective mechanism that allows organisms to develop resistance to subsequent insults. The conditioning effect occurs across organs and species. Recently, much attention has been given to remote ischemic limb conditioning due to its non-invasive nature and potential therapeutic applications. While tolerance is induced at the primary injury site (e.g. the heart in cardiac ischemia and the brain in stroke), the site of conditioning application is away from the target organ, suggesting the protective factors are extrinsic in nature rather than intrinsic. This review will focus on the peripheral factors that account for the induction of tolerance. Topics of particular interest are blood flow changes, peripheral neural pathways, humoral factors in circulation, and the peripheral immune system. This review will also discuss how conditioning may negatively affect metabolically compromised conditions, its optimal dose, and window for therapy development.

Remote ischemic conditioning during primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction: a systematic review and meta-analysis

Objective

This systematic review was designed to evaluate the efficacy of remote ischemic conditioning (RIC) with primary percutaneous coronary intervention (PCI) versus primary PCI alone for ST-segment elevation myocardial infarction (STEMI).

Search strategy

Computerized search for trials from PubMed, EMBASE, CENTRAL and Cochrane Database of Systematic Reviews databases.

Selection criteria

Trials investigating RIC plus primary PCI (group A) versus primary PCI alone (group B).

Outcome measures

Myocardial enzyme levels; left ventricular ejection fraction (LVEF); major adverse cardiac and cerebrovascular events (MACCEs); TIMI flow grade III; myocardial salvage index or infarct size per patients.

Results

In all, 14 studies involving 3165 subjects were included. There was a significant association of myocardial edema levels, myocardial salvage index and incidence of MACCEs in group A compared with group B (myocardial edema levels: SMD = − 0.36, 95% CI (− 0.59, − 0.13); myocardial salvage index: MD = 0.06, 95% CI (0.02, 0.10); MACCE: OR = 0.70, 95% CI (0.57, 0.85)). With regard to infarct size, TIMI flow grade III and LVEF, group A appeared to be equivalent with group B (infarct size: MD = − 1.67, 95% CI (− 3.46, 0.11); TIMI flow grade III: OR = 1.04, 95% CI (0.71, 1.52); LVEF: MD = 0.74, 95% CI (− 0.80, 2.28)).

Conclusion

RIC was associated with lower myocardial edema levels, myocardial salvage index and incidence of MACCE, while non-significant beneficial effect on infarct size, TIMI flow grade III or LVEF. These findings suggest that RIC is a promising adjunctive treatment to PCI for the prevention of reperfusion injury in STEMI patients.

Remote Limb Ischemic Conditioning and Motor Learning: Evaluation of Factors Influencing Response in Older Adults

Remote limb ischemic conditioning (RLIC) is a clinically feasible method of promoting tissue protection against subsequent ischemic insult. Recent findings from our lab demonstrated that RLIC robustly enhances motor learning in young, healthy humans. The next step is to determine which individuals would receive maximum benefit from RLIC before applying these findings to clinical rehabilitation populations such as stroke. Numerous factors, such as age, sex, body mass index (BMI), and cardiovascular comorbidities may influence the response. Sixty-nine participants aged 40-80 were randomized to receive either RLIC (n = 33) or sham (n = 36) conditioning. Participants underwent seven consecutive sessions consisting of RLIC or sham conditioning with a blood pressure cuff on the upper extremity and motor training on a stability platform balance task, with two follow-up sessions. Balance change (post-test-pre-test) was compared across participants, groups, and the factors of age, sex, BMI, and comorbidities. Participants in both groups improved their performance on the balance task from pre- to post-test. Overall balance change was independently associated with age and BMI. There was no difference in balance change between RLIC and Sham groups. However, RLIC significantly enhanced balance performance in participants with no comorbidities. Compared with our previous study in young adults, middle-aged and older adults demonstrated smaller improvements on the balance task. RLIC enhanced learning in middle-aged and older adults only in the absence of pre-defined comorbidities. RLIC may be a promising tool for enhancing motor recovery, but the accumulation of comorbidity with age may decrease its effectiveness.

Remote ischemic preconditioning fails to reduce infarct size in the Zucker fatty rat model of type-2 diabetes: role of defective humoral communication

Remote ischemic preconditioning (RIPC), the phenomenon whereby brief ischemic episodes in distant tissues or organs render the heart resistant to infarction, has been exhaustively demonstrated in preclinical models. Moreover, emerging evidence suggests that exosomes play a requisite role in conveying the cardioprotective signal from remote tissue to the myocardium. However, in cohorts displaying clinically common comorbidities-in particular, type-2 diabetes-the infarct-sparing effect of RIPC may be confounded for as-yet unknown reasons. To investigate this issue, we used an integrated in vivo and in vitro approach to establish whether: (1) the efficacy of RIPC is maintained in the Zucker fatty rat model of type-2 diabetes, (2) the humoral transfer of cardioprotective triggers initiated by RIPC are transported via exosomes, and (3) diabetes is associated with alterations in exosome-mediated communication. We report that a standard RIPC stimulus (four 5-min episodes of hindlimb ischemia) reduced infarct size in normoglycemic Zucker lean rats, but failed to confer protection in diabetic Zucker fatty animals. Moreover, we provide novel evidence, via transfer of serum and serum fractions obtained following RIPC and applied to HL-1 cardiomyocytes subjected to hypoxia-reoxygenation, that diabetes was accompanied by impaired humoral communication of cardioprotective signals. Specifically, our data revealed that serum and exosome-rich serum fractions collected from normoglycemic rats attenuated hypoxia-reoxygenation-induced HL-1 cell death, while, in contrast, exosome-rich samples from Zucker fatty rats did not evoke protection in the HL-1 cell model. Finally, and unexpectedly, we found that exosome-depleted serum from Zucker fatty rats was cytotoxic and exacerbated hypoxia-reoxygenation-induced cardiomyocyte death.

FGF-16 protects against adverse cardiac remodeling in the infarct diabetic heart

Till now, no functional studies for FGF-16 in diabetic heart have been reported. Therefore, this study aims to evaluate the potential function of FGF-16 in inhibiting adverse cardiac remodeling in post myocardial infarction (MI) of diabetic heart. We investigated the role of fibroblast growth factor-16 (FGF-16) in post-MI remodeling and role of cardio-protection in the diabetic infarct heart. Adult db/db diabetic mice were assigned to sham group, MI group and MI+FGF-16 group, respectively. MI group was induced by permanent coronary artery ligation, and the mice were subjected to 2D trans-thoracic echocardiography 2-4 weeks post-surgery. The results showed that the infiltration of monocytes, the associated pro-inflammatory cytokines were significantly increased, and the adverse cardiac remodeling and left ventricular dysfunction were observed in MI group. FGF-16 treatment protected against apoptosis, cardiac dysfunction and chamber dilatation post-MI, and decreased monocyte infiltration and cardiomyocyte hypertrophy/apoptosis. Meanwhile, the FGF-16 treatment also attenuated interstitial fibrosis and myocardial inflammation post-MI, increased M2 macrophage differentiation and associated anti-inflammatory cytokines, reduced adverse remodeling, and improved cardiac function. In conclusion, our results suggest that the heart appears to be a target of systemic and possibly locally generated FGF-16, which plays a therapeutic role in cardiac protection in the post-MI diabetic heart.

Myocardial susceptibility to ischaemia/reperfusion in obesity: a re-evaluation of the effects of age

Background

Reports on the effect of age and obesity on myocardial ischaemia/reperfusion (I/R) injury and ischaemic preconditioning are contradictory. The aim of this study was to re-evaluate the effects of age and diet-induced obesity (DIO) on myocardial I/R injury and preconditioning potential.

Methods

Four groups of Wistar male rats were used: age-matched controls (AMC) receiving standard rat chow for (i) 16 weeks and (ii) 16 months respectively; DIO rats receiving a sucrose-supplemented diet for (iii) 16 weeks and (iv) 16 months respectively. The ages of groups (i) and (iii) were 22 weeks (“young”) and groups (ii) and (iv) 17 months (“middle-aged”) at time of experimentation. Isolated perfused working hearts were subjected to 35 min regional ischaemia/1 h reperfusion. Endpoints were infarct size (tetrazolium staining) and functional recovery. Hearts were preconditioned by 3 × 5 min ischaemia/5 min reperfusion. Results were processed using GraphPad Prism statistical software.

Results

Age did not affect baseline heart function before induction of ischaemia and I/R damage as indicated by infarct size and similar values were obtained in hearts from both age groups. Age also had no effect on functional recovery of hearts during reperfusion after regional ischaemia in AMC rats, but cardiac output during reperfusion was better in hearts from middle-aged than young DIO rats.

The diet reduced infarct size in hearts from young rats (% of area at risk: AMC: 32.4 ± 3.6; DIO: 20.7 ± 2.9, p < 0.05), with no differences in hearts from middle-aged rats (AMC: 24.6 ± 4.6; DIO: 28.3 ± 13.5, p = NS). Compared to their respective AMC, diet-induced obesity had no significant effect on functional recovery of hearts from both age groups after exposure to regional ischaemia.

When exposed to the more severe stress of global ischaemia, the functional recovery potential of middle-aged DIO rats appeared to be impeded compared to hearts of young DIO rats, while age had no effect on the functional recovery of AMC hearts.

Preconditioning reduced infarct size in hearts from young control rats and both middle-aged groups, but not from young DIO rats. Age had a significant effect on functional recovery in preconditioning: it was improved in hearts from young control and DIO rats, but depressed in both middle-aged groups.

Conclusions

The data showed that middle-age and obesity had no effect on baseline myocardial function and did not increase susceptibility to I/R damage upon exposure to regional ischaemia. On the contrary, obesity reduced I/R damage in young rats. Preconditioned aging hearts showed a decreased infarct size, but a reduction in functional recovery.

Sarcolemmal dependence of cardiac protection and stress-resistance: roles in aged or diseased hearts

Disruption of the sarcolemmal membrane is a defining feature of oncotic death in cardiac ischaemia-reperfusion (I-R), and its molecular makeup not only fundamentally governs this process but also affects multiple determinants of both myocardial I-R injury and responsiveness to cardioprotective stimuli. Beyond the influences of membrane lipids on the cytoprotective (and death) receptors intimately embedded within this bilayer, myocardial ionic homeostasis, substrate metabolism, intercellular communication and electrical conduction are all sensitive to sarcolemmal makeup, and critical to outcomes from I-R. As will be outlined in this review, these crucial sarcolemmal dependencies may underlie not only the negative effects of age and common co-morbidities on myocardial ischaemic tolerance but also the on-going challenge of implementing efficacious cardioprotection in patients suffering accidental or surgically induced I-R. We review evidence for the involvement of sarcolemmal makeup changes in the impairment of stress-resistance and cardioprotection observed with ageing and highly prevalent co-morbid conditions including diabetes and hypercholesterolaemia. A greater understanding of membrane changes with age/disease, and the inter-dependences of ischaemic tolerance and cardioprotection on sarcolemmal makeup, can facilitate the development of strategies to preserve membrane integrity and cell viability, and advance the challenging goal of implementing efficacious 'cardioprotection' in clinically relevant patient cohorts. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

Remote ischaemic conditioning in the context of type 2 diabetes and neuropathy: the case for repeat application as a novel therapy for lower extremity ulceration

An emerging treatment modality for reducing damage caused by ischaemia–reperfusion injury is ischaemic conditioning. This technique induces short periods of ischaemia that have been found to protect against a more significant ischaemic insult. Remote ischaemic conditioning (RIC) can be administered more conveniently and safely, by inflation of a pneumatic blood pressure cuff to a suprasystolic pressure on a limb. Protection is then transferred to a remote organ via humoral and neural pathways. The diabetic state is particularly vulnerable to ischaemia–reperfusion injury, and ischaemia is a significant cause of many diabetic complications, including the diabetic foot. Despite this, studies utilising ischaemic conditioning and RIC in type 2 diabetes have often been disappointing. A newer strategy, repeat RIC, involves the repeated application of short periods of limb ischaemia over days or weeks. It has been demonstrated that this improves endothelial function, skin microcirculation, and modulates the systemic inflammatory response. Repeat RIC was recently shown to be beneficial for healing in lower extremity diabetic ulcers. This article summarises the mechanisms of RIC, and the impact that type 2 diabetes may have upon these, with the role of neural mechanisms in the context of diabetic neuropathy a focus. Repeat RIC may show more promise than RIC in type 2 diabetes, and its potential mechanisms and applications will also be explored. Considering the high costs, rates of chronicity and serious complications resulting from diabetic lower extremity ulceration, repeat RIC has the potential to be an effective novel advanced therapy for this condition.

Type 2 diabetes mellitus and myocardial ischemic preconditioning in symptomatic coronary artery disease patients

Background

The influence of diabetes mellitus on myocardial ischemic preconditioning is not clearly defined. Experimental studies are conflicting and human studies are scarce and inconclusive.

Objectives

Identify whether diabetes mellitus intervenes on ischemic preconditioning in symptomatic coronary artery disease patients.

Methods

Symptomatic multivessel coronary artery disease patients with preserved systolic ventricular function and a positive exercise test underwent two sequential exercise tests to demonstrate ischemic preconditioning. Ischemic parameters were compared among patients with and without type 2 diabetes mellitus. Ischemic preconditioning was considered present when the time to 1.0 mm ST deviation and rate pressure-product were greater in the second of 2 exercise tests. Sequential exercise tests were analyzed by 2 independent cardiologists.

Results

Of the 2,140 consecutive coronary artery disease patients screened, 361 met inclusion criteria, and 174 patients (64.2 ± 7.6 years) completed the study protocol. Of these, 86 had the diagnosis of type 2 diabetes. Among diabetic patients, 62 (72 %) manifested an improvement in ischemic parameters consistent with ischemic preconditioning, whereas among nondiabetic patients, 60 (68 %) manifested ischemic preconditioning (p = 0.62). The analysis of patients who demonstrated ischemic preconditioning showed similar improvement in the time to 1.0 mm ST deviation between diabetic and nondiabetic groups (79.4 ± 47.6 vs 65.5 ± 36.4 s, respectively, p = 0.12). Regarding rate pressure-product, the improvement was greater in diabetic compared to nondiabetic patients (3011 ± 2430 vs 2081 ± 2139 bpm x mmHg, respectively, p = 0.01).

Conclusions

In this study, diabetes mellitus was not associated with impairment in ischemic preconditioning in symptomatic coronary artery disease patients. Furthermore, diabetic patients experienced an improvement in this significant mechanism of myocardial protection.

Ischaemic conditioning: pitfalls on the path to clinical translation

The development of novel adjuvant strategies capable of attenuating myocardial ischaemia-reperfusion injury and reducing infarct size remains a major, unmet clinical need. A wealth of preclinical evidence has established that ischaemic 'conditioning' is profoundly cardioprotective, and has positioned the phenomenon (in particular, the paradigms of postconditioning and remote conditioning) as the most promising and potent candidate for clinical translation identified to date. However, despite this preclinical consensus, current phase II trials have been plagued by heterogeneity, and the outcomes of recent meta-analyses have largely failed to confirm significant benefit. As a result, the path to clinical application has been perceived as 'disappointing' and 'frustrating'. The goal of the current review is to discuss the pitfalls that may be stalling the successful clinical translation of ischaemic conditioning, with an emphasis on concerns regarding: (i) appropriate clinical study design and (ii) the choice of the 'right' preclinical models to facilitate clinical translation.

Lung protective effects of budesonide nebulization during perioperative period of thoracolumbar fusion

OBJECTIVE

To determine the pulmonary protective effect of budesonide nebulization in patients undergoing spinal fusion for thoracolumbar degenerative disorders.

METHODS

Forty patients who underwent spinal fusion at our hospital from January 2013 to December 2013 for the treatment of thoracolumbar degenerative disorders were randomly allocated into a budesonide intervention group (budesonide group) and a control group. The control group received routine supportive therapy including rehydration, analgesia, and neurotrophic drug treatment; in addition to these, the budesonide group was administered with budesonide nebulization (1-mg budesonide/2-mL saline, twice daily) from 1 day preoperatively through 3 days postoperatively. Respiratory symptoms, arterial blood gas, and pulmonary complication before and after the operations were observed and compared between the two groups.

RESULTS

The patients ranged in age from 46 to 81 years old (mean, 62.4±9.4 years), and comprised 20 men and 20 women. There were no significant differences in postoperative body temperature, heart rate, and respiratory rate between the groups (P>0.05). The change in arterial partial pressure of oxygen (PaO2) from baseline was significantly lower in the budesonide group than in the control group (at 2.4±12.4 vs. 16.0±11.3 mmHg) (P=0.002), so was the findings for oxygen saturation (SpO2) (0.2%±2.3% vs. 2.6%±3.3%), respectively (P=0.047). The incidence of postoperative pulmonary symptoms and complications, such as coughing, shortness of breath, and dyspnea, was 0% in the budesonide group and 15% in the control group; overall, the budesonide group performed better than control group in all pulmonary parameters. None of the patients in the budesonide group experienced severe events associated with glucocorticoid therapy.

CONCLUSIONS

Perioperative budesonide nebulization may reduce the postoperative pulmonary complications in middle-aged and elderly patients undergoing thoracolumbar fusion to treat thoracolumbar degeneration, with favorable efficacy and safety.