Glucose-Insulin-Potassium for Acute Myocardial Infarction: Continuing Controversy Over Cardioprotection

Insulin mitigates acute ischemia-induced atrial fibrillation and sinoatrial node dysfunction ex vivo

Acute atrial ischemia is a well-known cause of postoperative atrial fibrillation (POAF). However, mechanisms through which ischemia contributes to the development of POAF are not well understood. In this study, ex vivo Langendorff perfusion was used to induce acute ischemia/reperfusion in the heart to mimic POAF. Inducibility of atrial fibrillation (AF) was evaluated using programmed electrical stimulation and verified with open-atrium optical mapping. Compared with the control group without ischemia, 25 minutes of ischemia substantially increased the incidence of AF. The right atrium was more susceptible to AF than the left atrium. Administering insulin for 30 minutes before ischemia and during reperfusion with 25 minutes of ischemia greatly reduced the vulnerability to AF. However, insulin treatment during reperfusion only did not show substantial benefits against AF. Optical mapping studies showed that insulin mitigated ischemia-induced abnormal electrophysiology, including shortened action potential duration and effective refractory period, slowed conduction velocity, increased conduction heterogeneity, and altered calcium transients. In conclusion, insulin reduced the risk of acute ischemia/reperfusion-induced AF via improving the electrophysiology and calcium handling of atrial cardiomyocytes, which provides a potential therapy for POAF.

Association of dysglycaemia with persistent infarct core iron in patients with acute ST-segment elevation myocardial infarction

BACKGROUND

Dysglycaemia increases the risk of myocardial infarction and subsequent recurrent cardiovascular events. However, the role of dysglycaemia in ischemia/reperfusion injury with development of irreversible myocardial tissue alterations remains poorly understood. In this study we aimed to investigate the association of ongoing dysglycaemia with persistence of infarct core iron and their longitudinal changes over time in patients undergoing primary percutaneous coronary intervention (PCI) for acute ST-segment elevation myocardial infarction (STEMI).

METHODS

We analyzed 348 STEMI patients treated with primary PCI between 2016 and 2021 that were included in the prospective MARINA-STEMI study (NCT04113356). Peripheral venous blood samples for glucose and glycated hemoglobin (HbA1c) measurements were drawn on admission and 4 months after STEMI. Cardiac magnetic resonance (CMR) imaging including T2 * mapping for infarct core iron assessment was performed at both time points. Associations of dysglycaemia with persistent infarct core iron and iron resolution at 4 months were calculated using multivariable regression analysis.

RESULTS

Intramyocardial hemorrhage was observed in 147 (42%) patients at baseline. Of these, 89 (61%) had persistent infarct core iron 4 months after infarction with increasing rates across HbA1c levels (<5.7%: 33%, ≥5.7: 79%). Persistent infarct core iron was independently associated with ongoing dysglycaemia defined by HbA1c at 4 months (OR: 7.87 [95% CI: 2.60-23.78]; p < 0.001), after adjustment for patient characteristics and CMR parameters. The independent association was present even after exclusion of patients with diabetes (pre- and newly diagnosed, n = 16).

CONCLUSIONS

In STEMI patients treated with primary PCI, ongoing dysglycaemia defined by HbA1c is independently associated with persistent infarct core iron and a lower likelihood of iron resolution. These findings suggest a potential association between ongoing dysglycaemia and persistent infarct core iron, which warrants further investigation for therapeutic implications.

Takotsubo Cardiomyopathy: Current Treatment

Management of takotsubo syndrome (TTS) is currently empirical and supportive, via extrapolation of therapeutic principles worked out for other cardiovascular pathologies. Although it has been emphasized that such non-specific therapies for TTS are consequent to its still elusive pathophysiology, one wonders whether it does not necessarily follow that the absence of knowledge of TTS' pathophysiological underpinnings should prevent us for searching, designing, or even finding, therapies efficacious for its management. Additionally, it is conceivable that therapy for TTS may be in response to pathophysiological/pathoanatomic/pathohistological consequences (e.g., "myocardial stunning/reperfusion injury"), common to both TTS and coronary artery disease, or other cardiovascular disorders). The present review outlines the whole range of management principles of TTS during its acute phase and at follow-up, including considerations pertaining to the recurrence of TTS, and commences with the idea that occasionally management of TTS should consist of mere observation along the "first do no harm" principle, while self-healing is under way. Finally, some new therapeutic hypotheses (i.e., large doses of insulin infusions in association with the employment of intravenous short- and ultrashort-acting β-blockers) are being entertained, based on previous extensive animal work and limited application in patients with neurogenic cardiomyopathy and TTS.

Myocardial remote ischemic preconditioning: from cell biology to clinical application

Remote ischemic preconditioning (rIPC) is a cardioprotective phenomenon where brief periods of ischemia followed by reperfusion of one organ/tissue can confer subsequent protection against ischemia/reperfusion injury in other organs, such as the heart. It involves activation of humoral, neural or systemic communication pathways inducing different intracellular signals in the heart. The main purpose of this review is to summarize the possible mechanisms involved in the rIPC cardioprotection, and to describe recent clinical trials to establish the efficacy of these strategies in cardioprotection from lethal ischemia/reperfusion injury. In this sense, certain factors weaken the subcellular mechanisms of rIPC in patients, such as age, comorbidities, medication, and anesthetic protocol, which could explain the heterogeneity of results in some clinical trials. For these reasons, further studies, carefully designed, are necessary to develop a clearer understanding of the pathways and mechanism of early and late rIPC. An understanding of the pathways is important for translation to patients.

Co-morbidities and co-medications as confounders of cardioprotection-Does it matter in the clinical setting?

The translation of cardioprotection from robust experimental evidence to beneficial clinical outcome for patients suffering acute myocardial infarction or undergoing cardiovascular surgery has been largely disappointing. The present review attempts to critically analyse the evidence for confounders of cardioprotection in patients with acute myocardial infarction and in patients undergoing cardiovascular surgery. One reason that has been proposed to be responsible for such lack of translation is the confounding of cardioprotection by co-morbidities and co-medications. Whereas there is solid experimental evidence for such confounding of cardioprotection by single co-morbidities and co-medications, the clinical evidence from retrospective analyses of the limited number of clinical data is less robust. The best evidence for interference of co-medications is that for platelet inhibitors to recruit cardioprotection per se and thus limit the potential for further protection from myocardial infarction and for propofol anaesthesia to negate the protection from remote ischaemic conditioning in cardiovascular surgery. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Mouse models of atherosclerosis and their suitability for the study of myocardial infarction

Atherosclerotic plaques impair vascular function and can lead to arterial obstruction and tissue ischaemia. Rupture of an atherosclerotic plaque within a coronary artery can result in an acute myocardial infarction, which is responsible for significant morbidity and mortality worldwide. Prompt reperfusion can salvage some of the ischaemic territory, but ischaemia and reperfusion (IR) still causes substantial injury and is, therefore, a therapeutic target for further infarct limitation. Numerous cardioprotective strategies have been identified that can limit IR injury in animal models, but none have yet been translated effectively to patients. This disconnect prompts an urgent re-examination of the experimental models used to study IR. Since coronary atherosclerosis is the most prevalent morbidity in this patient population, and impairs coronary vessel function, it is potentially a major confounder in cardioprotective studies. Surprisingly, most studies suggest that atherosclerosis does not have a major impact on cardioprotection in mouse models. However, a major limitation of atherosclerotic animal models is that the plaques usually manifest in the aorta and proximal great vessels, and rarely in the coronary vessels. In this review, we examine the commonly used mouse models of atherosclerosis and their effect on coronary artery function and infarct size. We conclude that none of the commonly used strains of mice are ideal for this purpose; however, more recently developed mouse models of atherosclerosis fulfil the requirement for coronary artery lesions, plaque rupture and lipoprotein patterns resembling the human profile, and may enable the identification of therapeutic interventions more applicable in the clinical setting.

Tsg101 Is Involved in the Sorting and Re-Distribution of Glucose Transporter-4 to the Sarcolemma Membrane of Cardiac Myocytes

Cardiac cells can adapt to pathological stress-induced energy crisis by shifting from fatty acid oxidation to glycolysis. However, the use of glucose-insulin-potassium (GIK) solution in patients undergoing cardiac surgery does not alleviate ischemia/reperfusion (I/R)-induced energy shortage. This indicates that insulin-mediated translocation of glucose transporter-4 (Glut-4) is impaired in ischemic hearts. Indeed, cardiac myocytes contain two intracellular populations of Glut-4: an insulin-dependent non-endosomal pool (also referred to as Glut-4 storage vesicles, GSVs) and an insulin-independent endosomal pool. Tumor susceptibility gene 101 (Tsg101) has been implicated in the endosomal recycling of membrane proteins. In this study, we aimed to examine whether Tsg101 regulated the sorting and re-distribution of Glut-4 to the sarcolemma membrane of cardiomyocytes under basal and ischemic conditions, using gain- and loss-of-function approaches. Forced overexpression of Tsg101 in mouse hearts and isolated cardiomyocytes could promote Glut-4 re-distribution to the sarcolemma, leading to enhanced glucose entry and adenosine triphosphate (ATP) generation in I/R hearts which in turn, attenuation of I/R-induced cardiac dysfunction. Conversely, knockdown of Tsg101 in cardiac myocytes exhibited opposite effects. Mechanistically, we identified that Tsg101 could interact and co-localize with Glut-4 in the sarcolemma membrane of cardiomyocytes. Our findings define Tsg101 as a novel regulator of cardiac Glut-4 trafficking, which may provide a new therapeutic strategy for the treatment of ischemic heart disease.

Myocardial Protection by Glucose-Insulin-Potassium in Moderate- to High-Risk Patients Undergoing Elective On-Pump Cardiac Surgery: A Randomized Controlled Trial

BACKGROUND

Low cardiac output syndrome is a main cause of death after cardiac surgery. We sought to assess the impact of glucose-insulin-potassium (GIK) to enhance myocardial protection in moderate- to high-risk patients undergoing on-pump heart surgery.

METHODS

A randomized controlled trial was performed in adult patients (Bernstein-Parsonnet score >7) scheduled for elective aortic valve replacement and/or coronary artery bypass surgery. Patients were randomized to GIK (20 IU of insulin, 10 mEq of potassium chloride in 50 mL of glucose 40%) or saline infusion given over 60 minutes on anesthetic induction. The primary end point was postcardiotomy ventricular dysfunction (PCVD), defined as new/worsening left ventricular dysfunction requiring inotropic support (≥120 minutes). Secondary end points were the intraoperative changes in left ventricular function as assessed by transoesophageal echocardiography, postoperative troponin levels, cardiovascular and respiratory complications, and intensive care unit and hospital length of stay.

RESULTS

From 224 randomized patients, 222 were analyzed (112 and 110 in the placebo and GIK groups, respectively). GIK pretreatment was associated with a reduced occurrence of PCVD (risk ratio [RR], 0.41; 95% confidence interval [CI], 0.25-0.66). In GIK-treated patients, the left systolic ventricular function was better preserved after weaning from bypass, plasma troponin levels were lower on the first postoperative day (2.9 ng·mL(-) [interquartile range {IQR}, 1.5-6.6] vs 4.3 ng·mL(-) [IQR, 2.4-8.2]), and cardiovascular (RR, 0.69; 95% CI, 0.50-0.89) and respiratory complications (RR, 0.5; 95% CI, 0.38-0.74) were reduced, along with a shorter length of stay in intensive care unit (3 days [IQR, 2-4] vs 3.5 days [IQR, 2-7]) and in hospital (14 days [IQR, 11-18.5] vs 16 days [IQR, 12.5-23.5]), compared with placebo-treated patients.

CONCLUSIONS

GIK pretreatment was shown to attenuate PCVD and to improve clinical outcome in moderate- to high-risk patients undergoing on-pump cardiac surgery.

Uncoupling protein 3 deficiency impairs myocardial fatty acid oxidation and contractile recovery following ischemia/reperfusion

Patients with insulin resistance and type 2 diabetes have poor cardiac outcomes following myocardial infarction (MI). The mitochondrial uncoupling protein 3 (UCP3) is down-regulated in the heart with insulin resistance. We hypothesized that decreased UCP3 levels contribute to poor cardiac recovery following ischemia/reperfusion (I/R). After confirming that myocardial UCP3 levels were systematically decreased by 20-49% in animal models of insulin resistance and type 2 diabetes, we genetically engineered Sprague-Dawley rats with partial loss of UCP3 (ucp3^+/-). Wild-type littermates (ucp3^+/+) were used as controls. Isolated working hearts from ucp3^+/- rats were characterized by impaired recovery of cardiac power and decreased long-chain fatty acid (LCFA) oxidation following I/R. Mitochondria isolated from ucp3^+/- hearts subjected to I/R in vivo displayed increased reactive oxygen species (ROS) generation and decreased respiratory complex I activity. Supplying ucp3^+/- cardiac mitochondria with the medium-chain fatty acid (MCFA) octanoate slowed electron transport through the respiratory chain and reduced ROS generation. This was accompanied by improvement of cardiac LCFA oxidation and recovery of contractile function post ischemia. In conclusion, we demonstrated that normal cardiac UCP3 levels are essential to recovery of LCFA oxidation, mitochondrial respiratory capacity, and contractile function following I/R. These results reveal a potential mechanism for the poor prognosis of type 2 diabetic patients following MI and expose MCFA supplementation as a feasible metabolic intervention to improve recovery of these patients at reperfusion.

Diabetes: Prevalence, prognosis and management of a potent cardiovascular risk factor

This review highlights the increased risk of cardiovascular disease and the dismal prognosis after acute coronary events when diabetes is present. Although there have been improvements in this area, diabetes still confers an increased risk. In order to achieve successful outcomes in individuals with diabetes, extensive treatment of risk factors and the use of all available evidence-based therapies are needed. In this context, glucose-lowering therapies and antithrombotic and revascularisation strategies are detailed in this review. Emerging data indicate that novel glucose-lowering drugs may impact cardiovascular outcome with mechanisms that are beyond glucose control. In addition, this review addresses hidden diabetes and impaired glucose tolerance in patients with acute and stable coronary artery disease and how they influence future cardiovascular risk.

Imaging porcine cardiac substrate selection modulations by glucose, insulin and potassium intervention: A hyperpolarized [1-13 C]pyruvate study

Cardiac metabolism has received considerable attention in terms of both diagnostics and prognostics, as well as a novel target for treatment. As human trials involving hyperpolarized magnetic resonance in the heart are imminent, we sought to evaluate the general feasibility of detection of an imposed shift in metabolic substrate utilization during metabolic modulation with glucose-insulin-potassium (GIK) infusion, and thus the limitations associated with this strategy, in a large animal model resembling human physiology. Four [1-¹³ C]pyruvate injections did not alter the blood pressure or ejection fraction over 180 min. Hyperpolarized [1-¹³ C]pyruvate conversion showed a generally high reproducibility, with intraclass correlation coefficients between the baseline measurements at 0 and 30 min as follows: lactate to pyruvate, 0.85; alanine to pyruvate, 1.00; bicarbonate to pyruvate, 0.83. This study demonstrates that hyperpolarized [1-¹³ C]pyruvate imaging is a feasible technique for cardiac studies and shows a generally high reproducibility in fasted large animals. GIK infusion increases the metabolic conversion of pyruvate to its metabolic derivatives lactate, alanine and bicarbonate, but with increased variability.

Possible increase in insulin resistance and concealed glucose-coupled potassium-lowering mechanisms during acute coronary syndrome documented by covariance structure analysis

Objective

Although glucose-insulin-potassium (GIK) therapy ought to be beneficial for ischemic heart disease in general, variable outcomes in many clinical trials of GIK in acute coronary syndrome (ACS) had a controversial impact. This study was designed to examine whether “insulin resistance” is involved in ACS and to clarify other potential intrinsic compensatory mechanisms for GIK tolerance through highly statistical procedure.

Methods and results

We compared the degree of insulin resistance during ACS attack and remission phase after treatment in individual patients (n = 104). During ACS, homeostasis model assessment of insulin resistance (HOMA-IR) values were significantly increased (P<0.001), while serum potassium levels were transiently decreased (degree of which was indicated by ΔK) (P<0.001). This finding provides a renewed paradox, as ΔK, a surrogate marker of intrinsic GIK cascade activation, probably reflects the validated glucose metabolism during ischemic attack. Indeed, multiple regression analysis revealed that plasma glucose level during ACS was positively correlated with ΔK (P = 0.026), whereas HOMA-IR had no impact on ΔK. This positive correlation between ΔK and glucose was confirmed by covariance structure analysis with a strong impact (β: 0.398, P = 0.015). Intriguingly, a higher incidence of myocardial infarction relative to unstable angina pectoris, as well as a longer hospitalization period were observed in patients with larger ΔK, indicating that ΔK also reflects disease severity of ACS.

Conclusions

Insulin resistance most likely increases during ACS; however, ΔK was positively correlated with plasma glucose level, which overwhelmed insulin resistance condition. The present study with covariance structure analysis suggests that there are potential endogenous glucose-coupled potassium lowering mechanisms, other than insulin, regulating glucose metabolism during ACS.

Non-diabetic clinical applications of insulin

BACKGROUND

Introducing a new drug to the market is a time-consuming process, is complex, and involves consumption of a lot of resources. Therefore, discovering new uses for the old drugs (i.e. drug repurposing) benefits the patients by providing them time-tested drugs. With developments in insulin therapy still happening, it is worth keeping up to date on trends in the use of this powerful glucose-lowering agent. The aim of this article is to explore the potential non-diabetic clinical applications of insulin.

METHODS

Literature survey was carried out through the various scientific journals publishing experimental and clinical research papers regarding the diverse applications of insulin other than in diabetes mellitus. These applications include both therapeutic as well as diagnostic uses of insulin. The relevant information collected from these publications was paraphrased in the present paper.

RESULTS

On studying the literature, the non-diabetic uses of insulin include the following: wound healing, parenteral nutrition, antiaging, body building, cardioprotection in acute coronary syndromes, insulin tolerance test to test the hypothalamo-pituitary-adrenal axis functioning, cell culture, cancer treatment, organ preservation, and management of septic shock, calcium channel, β-blocker overdose and other critical illnesses in intensive care units.

CONCLUSIONS

This review attempts to survey some interesting new applications of insulin other than in diabetes mellitus.

Glucagon-Like Peptide-1: A Promising Agent for Cardioprotection During Myocardial Ischemia

Glucagon-like peptide-1-(7-36) amide (GLP-1) is a human incretin hormone responsible for the release of insulin in response to food. Pre-clinical and human physiological studies have demonstrated cardioprotection from ischemia-reperfusion injury. It can reduce infarct size, ischemic left ventricular dysfunction, and myocardial stunning. GLP-1 receptor agonists have also been shown to reduce infarct size in myocardial infarction. The mechanism through which this protection occurs is uncertain but may include hijacking the subcellular pathways of ischemic preconditioning, modulation of myocardial metabolism, and hemodynamic effects including peripheral, pulmonary, and coronary vasodilatation. This review will assess the evidence for each of these mechanisms in turn. Challenges remain in successfully translating cardioprotective interventions from bench-to-bedside. The window of cardioprotection is short and timing of cardioprotection in the appropriate clinical setting is critically important. We will emphasize the need for high-quality, well-designed research to evaluate GLP-1 as a cardioprotective agent for use in real-world practice.

Trans-system mechanisms against ischemic myocardial injury

A mammalian organism possesses a hierarchy of naturally evolved protective mechanisms against ischemic myocardial injury at the molecular, cellular, and organ levels. These mechanisms comprise regional protective processes, including upregulation and secretion of paracrine cell-survival factors, inflammation, angiogenesis, fibrosis, and resident stem cell-based cardiomyocyte regeneration. There are also interactive protective processes between the injured heart, circulation, and selected remote organs, defined as trans-system protective mechanisms, including upregulation and secretion of endocrine cell-survival factors from the liver and adipose tissue as well as mobilization of bone marrow, splenic, and hepatic cells to the injury site to mediate myocardial protection and repair. The injured heart and activated remote organs exploit molecular and cellular processes, including signal transduction, gene expression, cell proliferation, differentiation, migration, mobilization, and/or extracellular matrix production, to establish protective mechanisms. Both regional and trans-system cardioprotective mechanisms are mediated by paracrine and endocrine messengers and act in coordination and synergy to maximize the protective effect, minimize myocardial infarction, and improve myocardial function, ensuring the survival and timely repair of the injured heart. The concept of the trans-system protective mechanisms may be generalized to other organ systems-injury in one organ may initiate regional as well as trans-system protective responses, thereby minimizing injury and ensuring the survival of the entire organism. Selected trans-system processes may serve as core protective mechanisms that can be exploited by selected organs in injury. These naturally evolved protective mechanisms are the foundation for developing protective strategies for myocardial infarction and injury-induced disorders in other organ systems.

Reversal of hyperglycemia: effects on nitric oxide signaling

BACKGROUND

Hyperglycemia in patients with acute coronary syndromes is associated with poor outcomes, and its rapid correction with insulin infusion has been shown to restore platelet responsiveness to nitric oxide and to suppress superoxide (O2(-)) generation. Thioredoxin-interacting protein has emerged recently as a pivotal modulator of hyperglycemia-induced inflammation, O2(-) production, and impairment of nitric oxide signaling, but it is not known whether its expression in platelets can be downregulated rapidly.

METHODS

In 12 hyperglycemic patients with acute coronary syndrome, we evaluated the putative role of thioredoxin-interacting protein suppression in the platelet nitric oxide response after reversal of hyperglycemia with insulin infusion.

RESULTS

Insulin infusion for 13.0 ± 0.8 (standard error of the mean) hours decreased blood glucose level from 16.6 ± 1.6 mmol/L to 8.7 ± 1.4 mmol/L (P = .002). This induced (1) sensitization of antiaggregatory response to nitric oxide (from 6.5% ± 7.7% to 39.7% ± 7.0%, P < .0001); (2) improved endothelial progenitor cell function (from a median of 45 to 180 colony-forming units, P < .05); and (3) decreases of whole blood reactive oxygen species content (P < .05). However, there was no significant suppression of platelet thioredoxin-interacting protein expression (mean decrease, 59 arbitrary units; 95% confidence interval, -193 to +74).

CONCLUSIONS

Correction of hyperglycemia in patients with acute coronary syndrome rapidly reverses oxidative stress, restoring both platelet nitric oxide responsiveness and endothelial progenitor cell function, but this process is largely or entirely independent of thioredoxin-interacting protein.

Cardioprotection for percutaneous coronary intervention--reperfusion quality as well as quantity

Ischaemia-reperfusion (IR) injury is an important cause of myocardial damage during percutaneous coronary intervention (PCI). There are few therapies in widespread clinical use which impact on IR injury and it remains an important and underutilized target for treatment in acute myocardial infarction. This review will examine the translational scientific evidence for ischaemic conditioning and pharmacological agents including conditioning mimetics such as cyclosporine, anti-inflammatory agents, and those which modify myocardial glucose metabolism. We will address the reasons why many trials have failed to demonstrate clinical benefit and emphasize the need to deliver the right therapy to the right patient, at the right time to achieve successful translation of cardioprotection from bench-to-bedside. We critique trial design and offer advice for future translational trials in the field to ensure that effective treatments can be demonstrated clinically to improve patient outcomes during PCI.

Citric Acid Cycle Intermediates in Cardioprotection

Over the last decade, there has been a concerted clinical effort to deliver on the laboratory promise that a variety of maneuvers can profoundly increase cardiac tolerance to ischemia and/or reduce additional damage consequent upon reperfusion. Here we will review the proximity of the metabolic approach to clinical practice. Specifically, we will focus on how the citric acid cycle is involved in cardioprotection. Inspired by cross-fertilization between fundamental cancer biology and cardiovascular medicine, a set of metabolic observations have identified novel metabolic pathways, easily manipulable in man, which can harness metabolism to robustly combat ischemia-reperfusion injury.

Quantifying cardiovascular disease risk factors in patients with psoriasis: a meta-analysis

BACKGROUND

In a previous meta-analysis on categorical data we found an association between psoriasis and cardiovascular disease and associated risk factors.

OBJECTIVES

To quantify the level of cardiovascular disease risk factors in order to provide additional data for the clinical management of the increased risk.

METHODS

This was a meta-analysis of observational studies with continuous outcome using random-effects statistics. A systematic search of studies published before 25 October 2012 was conducted using the databases Medline, EMBASE, International Pharmaceutical Abstracts, PASCAL and BIOSIS.

RESULTS

We included 59 studies with up to 18 666 cases and 50 724 controls. Psoriasis cases had a higher total cholesterol [weighted mean difference 8·83 mg dL(-1) , 95% confidence interval (CI) 2·94-14·72, P = 0·003 (= 0·23 mmol L(-1) )], higher low-density lipoprotein cholesterol [9·90 mg dL(-1) , 95% CI 1·56-18·20, P = 0·020 (= 0·25 mmol L(-1) )], higher triglyceride [16·32 mg dL(-1) , 95% CI 12·02-20·63, P < 0·001 (= 0·18 mmol L(-1) )], a higher systolic blood pressure (4·77 mmHg, 95% CI 1·62-7·92, P = 0·003), a higher diastolic blood pressure (2·99 mmHg, 95% CI 0·60-5·38, P = 0·014), higher body mass idex (0·73 kg m(-2) , 95% CI 0·37-1·09, P < 0·001), higher waist circumference (3·61 cm, 95% CI 2·12-5·10, P < 0·001), higher fasting glucose [3·52 mg dL(-1) , 95% CI 0·64-6·41, P = 0·017 (= 0·20 mmol L(-1) )], higher nonfasting glucose [11·70 mg dL(-1) , 95% CI 11·24-12·15, P < 0·001 (= 0·65 mmol L(-1) )] and a higher HbA1c [1·09 mmol mol(-1) , 95% CI 0·87-1·31, P < 0·001 (= 2·2%)].

CONCLUSIONS

From a preventive medicine perspective, the weighted mean differences between cases and controls are significant, and therefore relevant to the clinical management of patients with psoriasis.

Effective glycaemic control critically determines insulin cardioprotection against ischaemia/reperfusion injury in anaesthetized dogs

AIMS

Experimental evidence has shown significant cardioprotective effects of insulin, whereas clinical trials produced mixed results without valid explanations. This study was designed to examine the effect of hyperglycaemia on insulin cardioprotective action in a preclinical large animal model of myocardial ischaemia/reperfusion (MI/R).

METHODS AND RESULTS

Anaesthetized dogs were subjected to MI/R (30 min/4 h) and randomized to normal plasma insulin/euglycaemia (NI/NG), normal-insulin/hyperglycaemia (NI/HG), high-insulin/euglycaemia (HI/NG), and high-insulin/hyperglycaemia (HI/HG) achieved by controlled glucose/insulin infusion. Endogenous insulin production was abolished by peripancreatic vessel ligation. Compared with the control animals (NI/NG), hyperglycaemia (NI/HG) significantly aggravated MI/R injury. Insulin elevation at clamped euglycaemia (HI/NG) protected against MI/R injury as evidenced by reduced infarct size, decreased necrosis and apoptosis, and alleviated inflammatory and oxidative stress (leucocyte infiltration, myeloperoxidase, and malondialdehyde levels). However, these cardioprotective effects of insulin were markedly blunted in hyperglycaemic animals (HI/HG). In vitro mechanistic study in neonatal rat cardiomyocytes revealed that insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and Akt was significantly attenuated by high glucose, accompanied by markedly increased IRS-1 O-GlcNAc glycosylation following hypoxia/reoxygenation. Inhibition of hexosamine biosynthesis with 6-diazo-5-oxonorleucine abrogated high glucose-induced O-GlcNAc modification and inactivation of IRS-1/Akt as well as cell injury.

CONCLUSIONS

Our results, derived from a canine model of MI/R, demonstrate that hyperglycaemia blunts insulin protection against MI/R injury via hyperglycaemia-induced glycosylation and subsequent inactivation of insulin-signalling proteins. Our findings suggest that prevention of hyperglycaemia is critical for achieving maximal insulin cardioprotection for the ischaemic/reperfused hearts.

Current state of clinical translation of cardioprotective agents for acute myocardial infarction

There is continued interest in the concept of limiting myocardial infarct size with adjunctive agents administered along with reperfusion injury; however, there remains considerable controversy in the literature. The purpose of this article is to review the medical literature on clinical trials performed during the past 3 years that have attempted to reduce myocardial infarct size by administration of adjunctive therapies along with reperfusion therapy. A PubMed-driven literature search revealed a host of clinical trials focusing on the following prominent types of therapies: endogenous conditioning (postconditioning and remote ischemic conditioning); rapid cooling; pharmacological therapy (cyclosporine, abciximab, clopidogrel, tirofiban, erythropoietin, thrombus aspiration, adenosine, glucose-insulin-potassium, statins, antidiabetic agents, FX06, iron chelation, and ranolazine). Although there remains some controversy, quite a few of these studies showed that adjunctive therapy further reduced myocardial infarct size when coupled with reperfusion. Antiplatelet agents are emerging as some of the newest agents that seem to have cardioprotective capabilities. Postconditioning has become a bit more controversial in the clinical literature; remote conditioning, early and rapid cooling, adenosine, and ranolazine are intriguing therapies deserving of larger studies. Certain agents and maneuvers, such as erythropoietin, protein kinase C δ inhibitors, iron chelation, and intra-aortic balloon counterpulsation, perhaps should be retired. The correct adjunctive therapy administered along with reperfusion has the capability of further reducing myocardial injury during ST-segment-elevation myocardial infarction.

Usefulness of serum unbound free fatty acid levels to predict death early in patients with ST-segment elevation myocardial infarction (from the Thrombolysis In Myocardial Infarction [TIMI] II trial)

Circulating total free fatty acid (FFA) levels are elevated early in myocardial infarction (MI) and have been associated with an increase in mortality. We investigated the association of serum unbound FFA (FFAu) levels with mortality in patients presenting with ST-segment elevation MI in the Thrombolysis In Myocardial Infarction II trial. The Thrombolysis In Myocardial Infarction II trial enrolled patients within 4 hours of chest pain onset. The patients were treated with a recombinant tissue plasminogen activator within 1 hour of enrollment. The FFAu concentration was evaluated in serum samples from 1,834 patients obtained at baseline, before therapy. The FFAu level was an independent risk factor for death as early as at 1 day of hospitalization and continued to be an independent risk factor for the >3.8 years of follow-up. When adjusted for other cardiovascular risk factors, the FFAu levels in the fourth versus the first quartile remained an independent risk factor for death from MI (hazard ratio 5.0, 95% confidence interval 1.9 to 13.0), all cardiac death (hazard ratio 2.4, 95% confidence interval 1.3 to 4.4), and all-cause death (hazard ratio 1.9, 95% confidence interval 1.2 to 3.1). Women were twice as likely to be in the upper 2 FFAu quartiles and had approximately twice the rate of death as men. In conclusion, FFAu elevation is 1 of the earliest molecular biomarkers of mortality in patients with ST-segment elevation MI and was independent of other risk factors known to affect the outcomes after ST-segment elevation MI.

Optimising cardioprotection during myocardial ischaemia: targeting potential intracellular pathways with glucagon-like peptide-1

Coronary heart disease and type-2 diabetes are both major global health burdens associated with an increased risk of myocardial infarction (MI). Following MI, ischaemia-reperfusion injury (IRI) remains a significant contributor to myocardial injury at the cellular level. Research has focussed on identifying a strategy or intervention to minimise IRI to optimise reperfusion therapy, with the aim of delivering a superior clinical outcome. The incretin hormone glucagon-like peptide-1, already an established basis for the treatment of type-2 diabetes, also has the potential to protect against IRI. We explain the physiology and cellular processes involved in IRI, and the intracellular pathways activated by GLP-1, which could intercept IRI and deliver cardioprotection. The review also examines the current preclinical and clinical evidence for GLP-1 in cardioprotection and future directions for research as we look for an effective adjunctive treatment to minimise IRI.

Transient decrease in serum potassium level during ischemic attack of acute coronary syndrome: paradoxical contribution of plasma glucose level and glycohemoglobin

Background

Although a decrease in serum potassium level has been suggested to be a fairly common observation in acute coronary syndrome (ACS), there have so far been no definitive reports directly demonstrating the transient potassium decrease (the potassium dip) during ischemic attack of ACS compared to stable phase in individual patients. To understand the pathophysiological significance of the potassium dip, we examined the changes in serum potassium level throughout ischemic attack and evaluated the clinical factors affecting it.

Methods

The degree of the potassium dip during ischemic attack (as indicated by ΔK, ΔK = K at discharge − K on admission) was examined in 311 consecutive patients with ACS who required urgent hospitalization in our institution.

Results

Serum potassium level during ischemic attack was significantly decreased compared to that during stable phase (P < 0.001). Multiple regression analysis revealed that plasma glucose level during attack was the sole factor which was positively correlated with ΔK (P < 0.01), while HbA1c level was negatively correlated (P < 0.05). The medication profiles and renal function had no impact on ΔK. A longer hospitalization period, higher incidence of myocardial infarction and higher peak creatine kinase level were observed in patients with a larger ΔK.

Conclusions

We have clearly demonstrated that there is a transient decrease in serum potassium level during ischemic attack of ACS compared to stable phase. The degree of the potassium dip was tightly correlated with glucose level, which overwhelmed the diabetic condition, and it also indicates the disease severity. The present study therefore promotes awareness of the significance of monitoring potassium level in parallel with glucose level in patients with ACS.

Cardiomyocyte aldose reductase causes heart failure and impairs recovery from ischemia

Aldose reductase (AR), an enzyme mediating the first step in the polyol pathway of glucose metabolism, is associated with complications of diabetes mellitus and increased cardiac ischemic injury. We investigated whether deleterious effects of AR are due to its actions specifically in cardiomyocytes. We created mice with cardiac specific expression of human AR (hAR) using the α–myosin heavy chain (MHC) promoter and studied these animals during aging and with reduced fatty acid (FA) oxidation. hAR transgenic expression did not alter cardiac function or glucose and FA oxidation gene expression in young mice. However, cardiac overexpression of hAR caused cardiac dysfunction in older mice. We then assessed whether hAR altered heart function during ischemia reperfusion. hAR transgenic mice had greater infarct area and reduced functional recovery than non-transgenic littermates. When the hAR transgene was crossed onto the PPAR alpha knockout background, another example of greater heart glucose oxidation, hAR expressing mice had increased heart fructose content, cardiac fibrosis, ROS, and apoptosis. In conclusion, overexpression of hAR in cardiomyocytes leads to cardiac dysfunction with aging and in the setting of reduced FA and increased glucose metabolism. These results suggest that pharmacological inhibition of AR will be beneficial during ischemia and in some forms of heart failure.

Myocardial ischemia reperfusion injury: from basic science to clinical bedside

Myocardial ischemia reperfusion injury contributes to adverse cardiovascular outcomes after myocardial ischemia, cardiac surgery or circulatory arrest. Primarily, no blood flow to the heart causes an imbalance between oxygen demand and supply, named ischemia (from the Greek isch, restriction; and haema, blood), resulting in damage or dysfunction of the cardiac tissue. Instinctively, early and fast restoration of blood flow has been established to be the treatment of choice to prevent further tissue injury. Indeed, the use of thrombolytic therapy or primary percutaneous coronary intervention is the most effective strategy for reducing the size of a myocardial infarct and improving the clinical outcome. Unfortunately, restoring blood flow to the ischemic myocardium, named reperfusion, can also induce injury. This phenomenon was therefore termed myocardial ischemia reperfusion injury. Subsequent studies in animal models of acute myocardial infarction suggest that myocardial ischemia reperfusion injury accounts for up to 50% of the final size of a myocardial infarct. Consequently, many researchers aim to understand the underlying molecular mechanism of myocardial ischemia reperfusion injury to find therapeutic strategies ultimately reducing the final infarct size. Despite the identification of numerous therapeutic strategies at the bench, many of them are just in the process of being translated to bedside. The current review discusses the most striking basic science findings made during the past decades that are currently under clinical evaluation, with the ultimate goal to treat patients who are suffering from myocardial ischemia reperfusion-associated tissue injury.

Critical illness hyperglycemia in pediatric cardiac surgery

Critical illness hyperglycemia (CIH) is common in pediatric and adult intensive care units (ICUs). Children undergoing surgical repair or palliation of congenital cardiac defects are particularly at risk for CIH and its occurrence has been associated with increased morbidity and mortality in this population. Strict glycemic control through the use of intensive insulin therapy (IIT) has been shown to improve outcomes in some adult and pediatric studies, yet these findings have sparked controversy. The practice of strict glycemic control has been slow in extending to pediatric ICUs because of the documented increase in the incidence of hypoglycemia in patients treated with IIT. Protocol driven approaches with more liberal glycemic targets have been successfully validated in general and cardiac critical care pediatric patients with low rates of hypoglycemia. It is unknown whether a therapeutic benefit is obtained by keeping patients in this more liberal glycemic control target. Definitive randomized controlled trials of IIT utilizing these targets in critically ill children are ongoing.

Incidence, predictors, and prognostic value of intramyocardial hemorrhage lesions in ST elevation myocardial infarction

BACKGROUND

Intra myocardial hemorrhage lesions (IMH) are underdiagnosed complication of ST elevation myocardial infarction (STEMI). We sought to determine the incidence, predictors and the prognostic value of IMH in STEMI using cardiac MR imaging (CMR) techniques.

METHODS

We screened for inclusion consecutive patients with STEMI treated by percutaneous coronary intervention (PCI) within the first 12 hr of evolution. IMH lesions were identified on T2-weighted sequences on CMR between days 4 and 8 after PCI. Adverse cardiac events were defined as a composite of death + severe ventricular arrhythmias + acute coronary syndrome + acute heart failure.

RESULTS

N = 114 patients were included and n = 11 patients (10%) presented IMH lesions. Patients with IMH lesions had a larger myocardial infarction extent (25.6 ± 1.8 vs. 13.5 ± 1.0 % LV mass, P < 0.01), microvascular obstructive lesions extent (4.6 ± 1.0 vs. 1.3 ± 0.3% LV mass, P < 0.01) and lower LV ejection fraction (40.7 ± 2.3% vs. 50.7 ± 1.3%, P < 0.01). The value of glycemia at admission was an independent predictor of IMH development (Odd ratio 1.8 [1.1-2.8] per mmol l(-1), P = 0.01). The incidence of adverse cardiac events was higher in the IMH group than in the non-IMH group during the first year following STEMI (P = 0.01, log-rank analysis). Cox regression analysis identified the presence of IMH lesions as an independent predictor of adverse clinical outcome (Hazard Ratio = 2.8 [1.2-6.8], P = 0.02).

CONCLUSION

Our study indicates that IMH is a rare but severe finding in STEMI, associated with a larger myocardial infarction and a worse clinical outcome. Per-PCI glycemia might influence IMH development.

Scientific principles and clinical implications of perioperative glucose regulation and control

Development of hyperglycemia after major operations is very common and is modulated by many factors. These factors include perioperative metabolic state, intraoperative management of the patient, and neuroendocrine stress response to surgery. Acute insulin resistance also develops perioperatively and contributes significantly to hyperglycemia. Hyperglycemia is associated with poor outcomes in critically ill and postsurgical patients. A majority of the investigations use the term "hyperglycemia" very loosely and use varying thresholds for initiating treatment. Initial studies demonstrated improved outcomes in critically ill, postsurgical patients who received intensive glycemic control (IGC) (target serum glucose <110 mg/dL). These results were quickly extrapolated to other clinical areas, and IGC was enthusiastically recommended in the perioperative period. However, there are few studies investigating the value of intraoperative glycemic control. Moreover, recent prospective trials have not been able to show the benefit of IGC; neither an appropriate therapeutic glycemic target nor the true efficacy of perioperative glycemic control has been fully determined. Practitioners should also appreciate technical nuances of various glucose measurement techniques. IGC increases the risk of hypoglycemia significantly, which is not inconsequential in critically ill patients. Until further specific data are accumulated, it is prudent to maintain glucose levels <180 mg/dL in the perioperative period, and glycemic control should always be accompanied by close glucose monitoring.