Cardioprotection by glucose-insulin-potassium: dependence on KATP channel opening and blood glucose concentration before ischemia

Glucose-insulin-potassium alleviates uterine cramping pain following cesarean delivery: A randomized, controlled trial

Objectives

To explore the effect of glucose-insulin-potassium (GIK) therapy on uterine cramping pain (UCP) following cesarean delivery (CD).

Design

Single-center, randomized controlled study.

Setting

Second Affiliated Hospital of Army Medical University, Chongqing, China.

Participants

A total of 140 women, aged 20-40 years, who underwent CD with a transverse incision were randomly assigned to the GIK (P) or control (C) groups in a 1:1 ratio.

Interventions

GIK was intravenously administered to patients in Group P. Patients in Group C received normal saline (NS). After umbilical cord clamping, oxytocin was administered intravenously. The same GIK and NS regimens were administered on postoperative days 1 and 2, followed by oxytocin 10 min later.

Primary and secondary outcome measures

Following oxytocin administration, UCP was assessed using the visual analog scale (VAS), and the maximum VAS score (primary outcome) was recorded.

Results

Patients in Group P had significantly lower maximum VAS scores than those in Group C on postoperative days 1 (38.4 ± 21.1 vs. 52.3 ± 20.8, p < 0.001) and 2 (10 [0,30] vs. 30.5 [8.75,50], p < 0.001). Group P patients also had shorter pain duration on postoperative day 1 (39.6 ± 19.5 min vs. 50.6 ± 18.2 min, p = 0.001). Group P patients had a lower incidence of inadequate analgesia of UCP than Group C on days 1 (45.5% vs. 74.2%, p < 0.001) and 2 (10.6% vs. 47.0%, p < 0.001); the RRs for experiencing inadequate analgesia for UCP postpartum in Group P patients was 0.612 (95% CI: 0.454-0.826, p < 0.001) on day 1 and 0.226 (95% CI: 0.107-0.476, p < 0.001) on day 2. The absolute risk reduction (ARR) was 28.7%; thus number needed to treat (NNT) was 3 after rounding up. A subgroup analysis demonstrated that Group P patients undergoing repeat CD had lower maximum VAS scores for UCP on both postoperative days 1 and 2.

Conclusion

Our findings suggest that GIK can relieve UCP and shorten its duration. Our results provide information to facilitate the development of novel approaches for managing UCP.Clinical Trial Registration: This study was approved by the Medical Ethics Committee of Second Affiliated Hospital of Army Medical University (2020-109-01, 19/11/2020) and registered in the Chinese Clinical Trial Registry (http://www.chictr.org.cn, ChiCTR2100041607,01/01/2021).

Cardiac Preconditioning Effect of Ketamine-Dexmedetomidine versus Fentanyl-Propofol during Arrested Heart Revascularization

Background

Myocardial damage due to ischemia and reperfusion is still unavoidable during coronary surgery. Anesthetic agents have myocardial preconditioning effect. Ketamine has sympathomimetic effect, while dexmedetomidine has a sympatholytic effect in addition to anesthetic, analgesic, and anti-inflammatory properties of both the drugs. This study was carried out to compare ketamine-dexmedetomidine (KD) combination with fentanyl-propofol (FP) combination on the release of cardiac troponin T (cTnT) and outcome after coronary artery bypass graft.

Patients and Methods

Ninety adult patients who underwent coronary artery bypass grafting (CABG) were assigned to receive either KD base anesthesia (KD group) or FP anesthesia (FP group). Trends of high-sensitive cTnT, CK-MB, and serum cortisol were followed in the first postoperative 24 h. Other outcomes were vital signs, weaning from cardiopulmonary bypass, tracheal extubation time, and echocardiographic findings.

Results

There was a significant lower release of cTnT in KD group than FP group during its peak values at 6 h after aortic unclamping (92.01 ± 7.332 in KD versus 96.73 ± 12.532 ng.L^-1 P = 0.032). significant lower levels of serum cortisol levels were noted KD group than in FP group at 6 and 12 h after aortic unclamping P < 0.001. As regard tracheal extubation time, patients assigned to KD group extubated earlier than whom in FP group 202.22 ± 28.674 versus 304.67 ± 40.598 min respectively P < 0.001.

Conclusion

The use of KD during on-pump CABG confers better myocardial protective and anti-inflammatory effect than fentanyl propofol.

Myocardial protection in cardiac surgery: how limited are the options? A comprehensive literature review

For patients undergoing cardiopulmonary bypass, myocardial protection is a key for successful recovery and improved outcomes following cardiac surgery that requires cardiac arrest. Different solutions, components and modes of delivery have evolved over the last few decades to optimise myocardial protection. These include cold and warm and blood and crystalloid solution through antegrade, retrograde or combined cardioplegia delivery approach. However, each method has its own advantages and disadvantages, posing a challenge to establish a gold-standard cardioplegic solution with an optimised mode of delivery for enhanced myocardial protection during cardiac surgery. The aim of this review is to provide a brief history of the development of cardioplegia, explain the electrophysiological concepts behind myocardial protection in cardioplegia, analyse the current literature and summarise existing evidence that warrants the use of varying cardioplegic techniques. We provide a comprehensive and comparative overview of the effectiveness of each technique in achieving optimal cardioprotection and propose novel techniques for optimising myocardial protection in the future.

Glucose-insulin-potassium improves left ventricular performances after aortic valve replacement: a secondary analysis of a randomized controlled trial

Background

Patients with left ventricular (LV) hypertrophy may suffer ischemia-reperfusion injuries at the time of cardiac surgery with impairment in left ventricular function. Using transesophageal echocardiography (TEE), we evaluated the impact of glucose-insulin potassium (GIK) on LV performances in patients undergoing valve replacement for aortic stenosis.

Methods

In this secondary analysis of a double-blind randomized trial, moderate-to-high risk patients were assigned to receive GIK (20 IU insulin with 10 mEq KCL in 50 ml glucose 40%) or saline over 60 min upon anesthetic induction. The primary outcomes were the early changes in 2-and 3-dimensional left ventricular ejection fraction (2D and 3D-LVEF), peak global longitudinal strain (PGLS) and transmitral flow propagation velocity (Vp).

Results

At the end of GIK infusion, LV-FAC and 2D- and 3D-LVEF were unchanged whereas Vp (mean difference [MD + 7.9%, 95% confidence interval [CI] 3.2 to 12.5%; P <  0.001) increased compared with baseline values. After Placebo infusion, there was a decrease in LV-FAC (MD -2.9%, 95%CI − 4.8 to − 1.0%), 2D-LVEF (MD -2.0%, 95%CI − 2.8 to − 1.3%, 3D-LVEF (MD -3.0%, 95%CI − 4.0 to − 2.0%) and Vp (MD − 4.5 cm/s, 95%CI − 5.6 to − 3.3 cm/s).

After cardiopulmonary bypass, GIK pretreatment was associated with preserved 2D and 3D-LVEF (+ 0.4%, 95% 95%CI − 0.8 to 1.7% and + 0.4%, 95%CI − 1.3 to 2.0%), and PGLS (− 0.9, 95%CI − 1.6 to − 0.2) as well as higher Vp (+ 5.1 cm/s, 95%CI 2.9 to 7.3), compared with baseline. In contrast, in the Placebo group, 2D-LVEF (− 2.2%, 95%CI − 3.4 to − 1.0), 3D-LVEF (− 6.0%, 95%CI − 7.8 to − 4.2), and Vp (− 7.6 cm/s, 95%CI − 9.4 to − 5.9), all decreased after bypass.

Conclusions

Administration of GIK before aortic cross-clamping resulted in better preservation of systolic and diastolic ventricular function in patients with LV hypertrophy undergoing aortic valve replacement.

Trial registration

ClinicalTrials.gov: NCT00788242, registered on November 10, 2008.

Cardioprotection by ginseng: experimental and clinical evidence and underlying mechanisms

Protection of the ischemic and reperfused myocardium represents a major therapeutic challenge. Translating results from animal studies to the clinical setting has been disappointing, yet the need for effective intervention, particularly to limit heart damage following infarction or surgical procedures such as coronary artery bypass grafting, is substantial. Among the many compounds touted as cardioprotective agents is ginseng, a medicinal herb belonging to the genus Panax, which has been used as a medicinal agent for thousands of years, particularly in Asian societies. The biological actions of ginseng are very complex and reflect composition of many bioactive components, although many of the biological and therapeutic effects of ginseng have been attributed to the presence of steroid-like saponins termed ginsenosides. Both ginseng and many ginsenosides have been shown to exert cardioprotective properties in experimental models. There is also clinical evidence that traditional Chinese medications containing ginseng exert cardioprotective properties, although such clinical evidence is less robust primarily owing to the paucity of large-scale clinical trials. Here, we discuss the experimental and clinical evidence for ginseng, ginsenosides, and ginseng-containing formulations as cardioprotective agents against ischemic and reperfusion injury. We further discuss potential mechanisms, particularly as these relate to antioxidant properties.

Glycemia and the cardioprotective effects of insulin pre-conditioning in the isolated rat heart

BACKGROUND

While acute hyperglycemia has been shown to mitigate the beneficial effects of ischemic preconditioning, its effect on insulin-induced preconditioning remains unclear.

METHODS

The study was designed to test the hypothesis that acute hyperglycemia diminishes the cardioprotective effects following a 20-min pre-ischemic pre-conditioning with insulin in the isolated rat heart using the Langendorff system. Forty hearts were assigned to receive modified Krebs-Henseleit (KH) buffer containing 0.5 U/L insulin and 100 mg/dL glucose (InsG100, n = 10), KH buffer with 100 mg/dL glucose (G100, n = 10), KH buffer supplemented with 0.5 U/L insulin and 600 mg/dL glucose (InsG600, n = 10), or with 600 mg/dL glucose (G600, n = 10). To match the osmotic pressure of the InsG600 group, 27.5 mmol/L of mannitol was added to KH solution in the InsG100 and G100 group. The four groups were perfused with each solution for 20 min prior to 15 min of no-flow ischemia, and during 20 min of reperfusion. Only during the ischemic period the heart was paced at 222 beats/min. Measurements of heart rate, coronary flow and maximum of LV derivative of pressure development (dP/dt max) were recorded. Myocardial phospho-protein kinase B (p-Akt) and tumor necrosis factor-α (TNF-α) levels were assayed by enzyme-linked immunosorbent assay and sandwich ELISA, respectively following reperfusion.

RESULTS

After reperfusion, LV dP/dt max and heart rate in the InsG100 group was significantly higher than that in the other three groups. The myocardial p-Akt level in the InsG100 group was significantly elevated when compared to the InsG600 group at the end of reperfusion. The p-Akt levels in the InsG600 and InsG100 group were significantly higher than in the corresponding non-insulin groups.

CONCLUSIONS

Acute hyperglycemia diminishes the cardioprotective effects of insulin preconditioning in the isolated rat heart, possibly mediated through the suppression of myocardial Akt phosphorylation.

Glucose and Insulin Influences on Heart and Brain in Cardiac Surgery

The elective global ischemia of on-pump coronary artery bypass surgery contributes to the incidence of postoperative mortality, complications, and use of resources. In addition to cardiopulmonary bypass and techniques for myocardial protection such as aortic cross clamp, ventricular fibrillation, and cardioplegia, the administration of systemic glucose-insulinpotassium (GIK) in the perioperative period may act as both a metabolic modulator and potential inodilator. GIK may therefore serve to protect the myocardium and promote adequate cardiac and hemodynamic performance that would improve patient recovery. Cell, tissue, and animal experiments have determined a number of mechanisms of action by which this may be achieved, with increasing focus on insulin as the key component. The original concepts centered on GIK during or after ischemia switching metabolism away from that based on nonesterified fatty acids toward a more favorable glucose-based metabolism and thus improving the efficiency of adenosine triphosphate production and glycogen preservation. Insulin's ability to reduce intracellular fatty acid metabolism may also reduce cellular membrane damage. More recently other mechanisms have also been suggested, including osmotic, oxygen free radical scavenging, and antiapoptotic and anti-inflammatory effects. However, trials that have examined the role of GIK in cardiac surgery have been small, open label, and involved a wide variety of regimens. They have demonstrated improved glycogen preservation, reduced infarct size, reduced incidences of dysrhythmias, need for inotropic agents, and low cardiac output state, and overall reduced lengths of stay. The perceived need to achieve strict blood glucose control to reduce neurologic injury and improve overall mortality have conflicted with its practical difficulties, particularly during cold cardiopulmonary bypass, and the exact role of supplemental glucose administration and resulting hyperglycemia require re-examination.

Effect of glucose-insulin-potassium on hyperlactataemia in patients undergoing valvular heart surgery: A randomised controlled study

BACKGROUND

Hyperlactataemia represents oxygen imbalance in the tissues and its occurrence during cardiac surgery is associated with adverse outcomes. Glucose-insulin-potassium (GIK) infusion confers myocardial protection against ischaemia-reperfusion injury and has the potential to reduce lactate release while improving its clearance.

OBJECTIVES

The objective of this study is to compare the effect of GIK on the incidence of hyperlactataemia in patients undergoing valvular heart surgery.

DESIGN

A randomised controlled study.

SETTING

Single university teaching hospital.

PATIENTS

One hundred and six patients scheduled for elective valvular heart surgery with at least two of the known risk factors for hyperlactataemia.

INTERVENTION

Patients were randomly allocated to receive either GIK solution (insulin 0.1 IU kg(-1) h(-1) and an infusion of 30% dextrose and 80 mmol l(-1) potassium at 0.5 ml kg(-1) h(-1)) or 0.9% saline (control) throughout surgery.

MAIN OUTCOME MEASURES

The primary outcome was the incidence of hyperlactataemia (lactate ≥ 4 mmol l(-1)) during the operation and until 24 h after the operation. Secondary outcomes included haemodynamic parameters, use of vasopressor or inotropic drugs, and fluid balance until 24 h postoperatively. Postoperative morbidity endpoints were also assessed.

RESULTS

The incidences of hyperlactataemia were similar in the groups (32/53 patients in each of the control and GIK groups, P > 0.999). There were no intergroup differences in haemodynamic parameters, use of vasopressor and inotropic drugs, or fluid balance. The incidences of postoperative morbidity endpoints were similar in both groups.

CONCLUSION

Despite its theoretical advantage, GIK did not provide beneficial effects in terms of the incidence of hyperlactataemia or outcome in patients undergoing valvular heart surgery.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT01825720.

Insulin/NFκB protects against ischemia-induced necrotic cardiomyocyte death

In the heart, insulin controls key functions such as metabolism, muscle contraction and cell death. However, all studies have been focused on insulin action during reperfusion. Here we explore the cardioprotective action of this hormone during ischemia. Rat hearts were perfused ex vivo with an ischemia/reperfusion Langendorff model in absence or presence of insulin. Additionally, cultured rat cardiomyocytes were exposed to simulated ischemia in the absence or presence of insulin. Cytoprotective effects were measured by myocardial infarct size, trypan blue exclusion, released LDH and DNA fragmentation by flow cytometry. We found that insulin protected against cardiac ischemia ex vivo and in vitro. Moreover, insulin protected cardiomyocytes from simulated ischemia by reducing necrotic cell death. Protective effects of insulin were dependent of Akt and NFκB. These novel results show that insulin reduces ischemia-induced cardiomyocyte necrosis through an Akt/NF-κB dependent mechanism. These novel findings clarify the role of insulin during ischemia and further support its use in early GIK perfusion to treat myocardial infarction.

Experimental and clinical evidences for glucose control in intensive care: is infused glucose the key point for study interpretation?

Stress-induced hyperglycemia has been considered an adaptive mechanism to stress up to the first intensive insulin therapy trial, which showed a 34% reduction in relative risk of in-hospital mortality when normalizing blood glucose levels. Further trials had conflicting results and, at present, stress-induced hyperglycemia management remains non-consensual. These findings could be explained by discrepancies in trials, notably regarding the approach to treat hyperglycemia: high versus restrictive caloric intake. Stress-induced hyperglycemia is a frequent complication during intensive care unit stay and is associated with a higher mortality. It results from an imbalance between insulin and counter-regulatory hormones, increased neoglucogenesis, and the cytokine-induced insulin-resistant state of tissues. In this review, we summarize detrimental effects of hyperglycemia on organs in the critically ill (peripheric and central nervous, liver, immune system, kidney, and cardiovascular system). Finally, we show clinical and experimental evidence of potential benefits from glucose and insulin administration, notably on metabolism, immunity, and the cardiovascular system.

Multiplicity of effectors of the cardioprotective agent, diazoxide

Diazoxide has been identified over the past 50years to have a number of physiological effects, including lowering the blood pressure and rectifying hypoglycemia. Today it is used clinically to treat these conditions. More recently, another important mode of action emerged: diazoxide has powerful protective properties against cardiac ischemia. The heart has intrinsic protective mechanisms against ischemia injury; one of which is ischemic preconditioning. Diazoxide mimics ischemic preconditioning. The purpose of this treatise is to review the literature in an attempt to identify the many effectors of diazoxide and discuss how they may contribute to diazoxide's cardioprotective properties. Particular emphasis is placed on the concentration ranges in which diazoxide affects its different targets and how this compares with the concentrations commonly used to study cardioprotection. It is concluded that diazoxide may have several potential effectors that may potentially contribute to cardioprotection, including KATP channels in the pancreas, smooth muscle, endothelium, neurons and the mitochondrial inner membrane. Diazoxide may also affect other ion channels and ATPases and may directly regulate mitochondrial energetics. It is possible that the success of diazoxide lies in this promiscuity and that the compound acts to rebalance multiple physiological processes during cardiac ischemia.

An increase in the redox state during reperfusion contributes to the cardioprotective effect of GIK solution

This study aimed at determining whether glucose-insulin-potassium (GIK) solutions modify the NADH/NAD(+) ratio during postischemic reperfusion and whether their cardioprotective effect can be attributed to this change in part through reduction of the mitochondrial reactive oxygen species (ROS) production. The hearts of 72 rats were perfused with a buffer containing glucose (5.5 mM) and hexanoate (0.5 mM). They were maintained in normoxia for 30 min and then subjected to low-flow ischemia (0.5% of the preischemic coronary flow for 20 min) followed by reperfusion (45 min). From the beginning of ischemia, the perfusate was subjected to various changes: enrichment with GIK solution, enrichment with lactate (2 mM), enrichment with pyruvate (2 mM), enrichment with pyruvate (2 mM) plus ethanol (2 mM), or no change for the control group. Left ventricular developed pressure, heart rate, coronary flow, and oxygen consumption were monitored throughout. The lactate/pyruvate ratio of the coronary effluent, known to reflect the cytosolic NADH/NAD(+) ratio and the fructose-6-phosphate/dihydroxyacetone-phosphate (F6P/DHAP) ratio of the reperfused myocardium, were evaluated. Mitochondrial ROS production was also estimated. The GIK solution improved the recovery of mechanical function during reperfusion. This was associated with an enhanced cytosolic NADH/NAD(+) ratio and reduced mitochondrial ROS production. The cardioprotection was also observed when the hearts were perfused with fluids known to increase the cytosolic NADH/NAD(+) ratio (lactate, pyruvate plus ethanol) compared with the other fluids (control and pyruvate groups). The hearts with a high mechanical recovery also displayed a low F6P/DHAP ratio, suggesting that an accelerated glycolysis rate may be responsible for increased cytosolic NADH production. In conclusion, the cardioprotection induced by GIK solutions could occur through an increase in the cytosolic NADH/NAD(+) ratio, leading to a decrease in mitochondrial ROS production.

High-dose fasudil preserves postconditioning against myocardial infarction under hyperglycemia in rats: role of mitochondrial KATP channels

BACKGROUND

The current study was carried out to determine whether fasudil hydrochloride (fasudil), a Rho-kinase inhibitor, has myocardial postconditioning (PostC) activity under hyperglycemia as well as normoglycemia, and if so, whether the effects could be mediated by mitochondrial ATP-sensitive potassium (m-KATP) channels.

METHODS

Male Sprague-Dawley rats were anesthetized with sodium pentobarbital. After opening the chest, all rats underwent 30-min coronary artery occlusion followed by 2-h reperfusion. The rats received low-dose (0.15 mg/kg) or high-dose (0.5 mg/kg) fasudil or diazoxide, an m-KATP channel opener, at 10 mg/kg, just before reperfusion under normoglycemic or hyperglycemic conditions. In another group, rats received 5-hydroxydecanoic acid (5HD), an m-KATP channel blocker, at 10 mg/kg, before high-dose fasudil. Myocardial infarct size was expressed as a percentage of area at risk (AAR).

RESULTS

Under normoglycemia, low-dose and high-dose fasudil and diazoxide reduced myocardial infarct size (23 ± 8%, 21 ± 9% and 21 ± 10% of AAR, respectively) compared with that in the control (42 ± 7%). Under hyperglycemia, low-dose fasudil (40 ± 11%) and diazoxide (44 ± 14%) could not exert this beneficial effect, but high-dose fasudil reduced myocardial infarct size in the same manner as under normoglycemia (21 ± 13%). 5HD prevented fasudil-induced reduction of myocardial infarct size (42 ± 13%).

CONCLUSION

Fasudil induces PostC against myocardial infarction via activation of m-KATP channels in the rat. Although hyperglycemia attenuates the PostC, high-dose fasudil can restore cardioprotection.

High-dose insulin in experimental myocardial infarction in rabbits: protection against effects of hyperglycaemia

INTRODUCTION

Hyperglycaemia at the time of acute myocardial infarction (AMI) is a predictor of survival and is associated with increased mortality and morbidity in patients with or without diabetes mellitus. On the other hand, insulin has been shown to reduce myocardial injury in experimental studies but its benefits have not been confirmed in clinical studies.

METHODS

The isolated perfused heart model was used to examine the direct effect of incremental doses of insulin and varying degrees of hyperglycaemia on infarct size and cardiomyocyte apoptosis in rabbit hearts. The rabbit hearts were subjected to 30-min ischaemia and 2.5-h reperfusion.

RESULTS

Insulin, given alone just before reperfusion, dramatically reduced infarct size in a dose-dependent manner (75-300 μU/ml) during experimental myocardial infarction (46%±2% to 10.9%±3%, P<.001). Acutely elevated glucose levels (33 mmol/L) induced a significantly greater infarct size and cardiomyocyte apoptosis compared to hearts subjected to normal glucose levels. On the other hand, high-dose insulin (300 μU/ml) given 5 min before reperfusion attenuated the extent of infarction and reduced apoptosis in hearts that were exposed to high glucose levels.

CONCLUSION

Acutely elevated levels of glucose induced larger infarct area during ischaemia-reperfusion, and this is mediated through proapoptotic pathways. Insulin, when given just before reperfusion, confers cardioprotection in a dose-dependent manner and reverses the detrimental effect of acute hyperglycaemia. High-dose insulin as well as maintaining normoglycaemia remain important factors that improve outcomes following myocardial infarction.

Myocardial protection of insulin and potassium in a porcine ischemia-reperfusion model

BACKGROUND

We previously evaluated cardioprotective effects of glucose-insulin-potassium (GIK) in a porcine ischemia-reperfusion model; our results showed less myocardial pH decrease during ischemia and reperfusion and faster normalization of ATP and glucose during reperfusion. The proposed protective mechanism was facilitation of glucose transport for myocardial metabolism. The objective of this study was to assess the impact of insulin-potassium (IK) alone on myocardial metabolism.

METHODS

Male swine received continuous infusion of IK (IK group, n = 10), GIK (GIK group, n = 10), or standard lactated Ringer's (LR) solution (controls, n = 10). Induction of 20 minutes of ischemia in the left anterior descending (LAD) artery distribution was followed by 20 minutes of reperfusion. Real-time biosensors recorded pH and glucose levels in ischemic and nonischemic beds. Myocardial biopsies in the distribution of the LAD assessed ATP levels. Groups were compared using the Kruskal-Wallis and Mann-Whitney tests.

RESULTS

Real-time data are presented as percent change from baseline. At less than 10 minutes of ischemia, the average pH change was less for the IK group than the LR group (0.03% +/- 0.21% vs -2.06% +/- 1.23%; P = .001), and the pH change in the IK group was similar to the GIK group. After 10 minutes of ischemia and during the first 10 minutes of reperfusion, the IK group experienced pH changes that were similar to the LR group. Biopsies after 20 minutes of ischemia and 20 minutes of reperfusion showed less of a decline in ATP levels for the IK group compared to the LR group. Glucose at all time points demonstrated no statistically significant differences.

CONCLUSION

IK infusion alone demonstrates cardioprotective effects during early ischemia; however, compared to GIK infusion after 20 minutes of ischemia and reperfusion, myocardial pH and glucose levels were not sustained. Although insulin may facilitate glucose transport during ischemia, additional glucose in combination with IK enhances myocardial protection during reperfusion. This finding suggests that GIK enhancement during acute ischemia-reperfusion may improve myocardial protection.

Pharmacologic therapeutics for cardiac reperfusion injury

Cardiovascular disease is the leading cause of morbidity and mortality in industrial societies, with myocardial infarction as the primary assassin. Pharmacologic agents, including the myocardial cell membrane receptor agonists adenosine, bradykinin/angiotensin-converting enzyme inhibitors, opioids and erythropoietin or the mixed cell membrane and intracellular agonists, glucose insulin potassium, and volatile anesthetics, either clinically or experimentally reduce the extent of myocardial injury when administered just prior to reperfusion. Agents that specifically target proteins, transcription factors or ion channels, including PKC agonists/antagonists, PPAR, Phosphodiesterase-5 inhibitors, 3-Hydroxy-3-methyl glutaryl coenzyme A reductase and the ATP-dependent potassium channel are also promising. However, no agent has been specifically approved to reduce reperfusion injury clinically. In this review, we will discuss the advantages and limitations of agents to combat reperfusion injury, their market development status and findings reported in both clinical and preclinical studies. The molecular pathways activated by these agents that preserve myocardium from reperfusion injury, which appear to commonly involve glycogen synthase kinase 3beta and mitochondrial permeability transition pore inhibition, are also described.

Hyperglycemia during acute myocardial infarction in patients who are treated by primary percutaneous coronary intervention: impact on long-term prognosis

BACKGROUND

Transient hyperglycemia is common during acute myocardial infarction in non-diabetic patients and is associated with a worse outcome. There is limited data on the outcome of patients who undergo primary percutaneous coronary intervention and have transient hyperglycemia.

METHODS

Fasting plasma glucose was measured in 431 consecutive acute myocardial infarction patients who underwent primary percutaneous coronary interventions. Patients were classified into three groups: non-diabetics/non-hyperglycemic (NDNH, glucose < 126 mg/dL; n=224); non-diabetics/hyperglycemic (NDH, glucose > or = 126 mg/dL; n=119); and diabetics (n=88). Data were analyzed according to the different groups and according to exact glucose levels.

RESULTS

In-hospital mortality was significantly lower in NDNH (1%) compared to NDH (8%) and diabetic (5%) patients (p=0.01). One-year cumulative mortality was highest (10%) in patients with NDH (p<0.001). One year target lesion revascularization rates were identical in NDNH and NDH patients (6% vs. 8%) and higher in diabetic patients (19%, p=0.001). In a multivariate model, a striking increase in the risk of death (0.6%, p=0.05) and target lesion revascularization (2%, p<0.0001) was found for every increment of 1 mg/dL in glucose level.

CONCLUSIONS

Transient hyperglycemia in non-diabetic acute myocardial infarction patients who undergo primary percutaneous coronary interventions is associated with high one-year mortality. One year target lesion revascularization rates were significantly higher in diabetics compared to non-diabetics with normoglycemia or transient hyperglycemia.

Effects of glucose-insulin-potassium infusion on myocardial perfusion and left ventricular remodeling in patients treated with primary angioplasty for ST-elevation acute myocardial infarction

The role of glucose-insulin-potassium (GIK) infusion in the management of acute coronary syndrome is controversial. Limited data are available on the effects of adjunctive high-dose GIK (30% glucose, 50 IU of insulin, 80 mEq of potassium chloride infused at 1.5 ml/kg/hour over 24 hours) on myocardial perfusion and left ventricular (LV) remodeling in patients treated with primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction. In this prospective study, 73 patients were randomized to receive GIK infusion (n = 40) or saline (placebo, n = 33) in addition to standard therapy. The primary end points were myocardial perfusion after PCI and LV remodeling at 6 months. Thrombolysis In Myocardial Infarction frame count and myocardial blush grade were evaluated before and after reperfusion treatment. LV end-diastolic and end-systolic volumes, ejection fraction, and wall motion score index were assessed in each patient after PCI and after 6 months. Although no differences in final Thrombolysis In Myocardial Infarction flow were observed between the 2 groups, myocardial blush grade 3 was more frequently achieved in the GIK group (p <0.05). At 6 months, ventricular remodeling was more often observed in the control group (24% vs 3%, p <0.05). In conclusion, GIK infusion in adjunct to primary PCI in patients with ST-segment elevation myocardial infarction was safe, improved myocardial perfusion after revascularization, and was associated with less LV remodeling at follow-up.

Suppression of nitrative damage by metallothionein in diabetic heart contributes to the prevention of cardiomyopathy

Diabetic cardiomyopathy has become a major contributor to the increased mortality of diabetic patients. Although the development and progression of diabetic cardiomyopathy are considered to be associated with diabetes-derived oxidative stress, the precise mechanisms for and effectively preventive approaches to diabetic cardiomyopathy remain to be explored. Recent studies showed that reactive oxygen or nitrogen species (ROS/RNS) not only play a critical role in the initiation of diabetic cardiomyopathy, but also play an important role in physiological signaling. Therefore, this review will first discuss the dual roles of ROS/RNS in the physiological signaling and pathogenic remodeling leading to cardiomyopathy under diabetic conditions. The significant prevention of diabetic cardiomyopathy by metallothionein (MT) as a potent and nonspecific antioxidant will be also summarized. It is clearly revealed that although dual roles of peroxynitrite-nitrated proteins have been indicated under both physiological and pathogenic conditions, suppression of nitrative damage by MT in the diabetic heart is the major mechanism responsible for its prevention of diabetic cardiomyopathy. Finally the potential for clinical enhancement of the cardiac MT expression to prevent or delay the occurrence of cardiomyopathy in diabetic patients will also be addressed.

High glucose protects single beating adult cardiomyocytes against hypoxia

In the heart, the opening of sarcolemmal ATP-sensitive K(+) (K(ATP)) channels seems to be crucial for the cardiac protection against hypoxia/ischaemia. In the present study, we have exposed cardiomyocytes under hypoxia to high extracellular glucose (30 mM). Under these conditions, intracellular concentration of 1,3-bisphosphoglycerate has increased confirming stimulation of glycolysis. Perforated patch-clamp electrophysiology revealed that hypoxia induces whole-cell K(+) current in cardiomyocytes more efficiently in the presence than in the absence of high glucose. Glucose significantly promoted survival of cardiomyocytes exposed to hypoxia. HMR 1098, an antagonist of sarcolemmal K(ATP) channels, inhibited glucose-induced activation of whole-cell K(+) current during hypoxia as well as glucose-mediated cytoprotection. An inhibitor of glyceraldehyde 3-phosphate dehydrogenase, iodoacetate, inhibited glycolysis in hypoxia and blocked the activation of sarcolemmal K(ATP) channels. Based on the obtained results, we conclude that the activation of sarcolemmal K(ATP) channels is involved in glucose-mediated cardioprotection.

Improved myocardial protection during coronary artery surgery with glucose-insulin-potassium: A randomized controlled trial

OBJECTIVE

We sought to assess the role of glucose-insulin-potassium in providing myocardial protection in nondiabetic patients undergoing coronary artery surgery with cardiopulmonary bypass.

METHODS

A prospective, randomized, double-blind, placebo-controlled trial was conducted at a single-center university hospital performing adult cardiac surgery. Two hundred eighty nondiabetic adult patients undergoing first-time elective or urgent isolated multivessel coronary artery bypass grafting were prospectively randomized to receive glucose-insulin-potassium infusion or placebo (dextrose 5%) before, during, and for 6 hours after surgical intervention. Anesthetic, cardiopulmonary bypass, myocardial protection, and surgical techniques were standardized. The primary end point was postreperfusion cardiac index. Secondary end points were systemic vascular resistance index, the incidence of low cardiac output episodes, inotrope and vasoconstrictor use, and biochemical-electrocardiographic evidence of myocardial injury. The incidence of dysrhythmias and infections requiring treatment was recorded prospectively.

RESULTS

The glucose-insulin-potassium group experienced higher cardiac indices (P < .001) throughout infusion and reduced vascular resistance (P < .001). The incidence of low cardiac output episodes was 15.9% (22/138) in the glucose-insulin-potassium group and 27.5% (39/142) in the placebo group (P = .021). Inotropes were required in 18.8% (26/138) of the glucose-insulin-potassium group and 40.8% (58/142) of the placebo group (P < .001). Fewer patients in the glucose-insulin-potassium group (12.3% [16/133]) versus those in the placebo group (23.4% [32/137]) had significant myocardial injury (P = .017). Noncardiac morbidity was not different.

CONCLUSION

Glucose-insulin-potassium therapy improves early postoperative cardiovascular performance, reduces inotrope requirement, and might reduce myocardial injury. These potential benefits are not at the expense of increased noncardiac morbidity.

Isolated heart function during ischemia and reperfusion in sucrose-fed rats. Effect of insulin infusion

In myocardial damage due to ischemia-reperfusion, the administration of insulin together with glucose and potassium may be protective, although in some patients and animal models, it is ineffective. In a rat model (HTG) with characteristics of the metabolic syndrome, induced by sucrose feeding, ischemia-reperfusion of the isolated heart evidences a less favorable outcome than in control animals, particularly males. We investigated the effect of insulin infusion during the reperfusion period in isolated hearts from control and HTG male and female rats. Weanling Wistar rats were given commercial rat chow and tap water (C rats) or 30% sucrose solution (HTG rats) for 8 months. They developed moderate hypertension and hyperinsulinemia, central adiposity, nephropathy, and hypertriglyceridemia. Cardiac function was recorded in a Langendorff preparation subjected to 25 min ischemia and 15 min reperfusion. The handicapped functionality of HTG hearts is more apparent under conditions of stress. Insulin administration improved particularly mechanical work and +dp/dt max variables. The effect of sex was observed on the type of arrhythmias developed during reperfusion: Only the males showed lethal ventricular fibrillation, which disappeared after insulin administration. Females had lower levels of cardiac enzymes creatine kinase (CKMB) and lactic dehydrogenase (LDH), but their performance was not hindered, probably on account of protective factors such as estrogens. Summing up, the pathological features of the HTG model did not prevent insulin from exerting some of its beneficial effects in HTG hearts. Sex differences in the outcome were more apparent in the type of arrhythmias after reperfusion; they were lethal in HTG males only, but insulin prevented their onset.