The deleterious effects of hyperglycemia on platelet function in diabetic patients with acute coronary syndromes mediation by superoxide production, resolution with intensive insulin administration

Impact of hyperglycemia on myocardial ischemia-reperfusion susceptibility and ischemic preconditioning in hearts from rats with type 2 diabetes

Background

The mechanisms underlying increased mortality in patients with diabetes and admission hyperglycemia after an acute coronary syndrome may involve reduced capacity for cardioprotection. We investigated the impact of hyperglycemia on exogenously activated cardioprotection by ischemic preconditioning (IPC) in hearts from rats with type 2 diabetes mellitus (T2DM) that were endogenously cardioprotected by an inherent mechanism, and the involvement of myocardial glucose uptake (MGU) and myocardial O-linked β-N-acetylglucosamine (O-GlcNAc).

Methods and results

In isolated, perfused rat hearts subjected to ischemia–reperfusion, infarct size (IS) was overall larger during hyper- ([Glucose] = 22 mmol/L]) than normoglycemia ([Glucose] = 11 mmol/L]) (p < 0.001). IS was smaller in 12-week old Zucker diabetic fatty rats with recent onset T2DM (fa/fa) than in rats without T2DM (fa/+) (n = 8 in each group) both during hyperglycemia (p < 0.05) and normoglycemia (p < 0.05). IPC (2 × 5 min cycles) reduced IS during normo- (p < 0.01 for both groups) but not during hyperglycemia independently of the presence of T2DM. During hyperglycemia, an intensified IPC stimulus (4 × 5 min cycles) reduced IS only in hearts from animals with T2DM (p < 0.05). IPC increased MGU and O-GlcNAc levels during reperfusion in animals with and without T2DM at normoglycemia (MGU: p < 0.05, O-GlcNAc: p < 0.01 for both groups) but not during hyperglycemia. Intensified IPC at hyperglycemia increased MGU (p < 0.05) and O-GlcNAc levels (p < 0.05) only in hearts from animals with T2DM.

Conclusion

While the effect of IPC is reduced during hyperglycemia in rats without T2DM, endogenous cardioprotection in animals with T2DM is not influenced by hyperglycemia and the capacity for exogenous cardioprotection by IPC is preserved. MGU and O-GlcNAc levels are increased by exogenously induced cardioprotection by IPC but not by endogenous cardioprotection in animals with T2DM reflecting different underlying mechanisms by exogenous and endogenous cardioprotection.

Effect of stress hyperglycaemia on monocyte chemoattractant protein-1 levels and the short-term prognosis of patients with acute ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

The present study prospectively investigated the effect of blood glucose level at admission on monocyte chemoattractant protein-1 levels at different time points before and after primary percutaneous coronary intervention, and the postoperative 1-year prognosis of patients with acute ST-segment elevation myocardial infarction. The 146 patients with acute ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention were divided into three groups: Group 1, non-diabetic, non-hyperglycemic group; group 2, stress hyperglycemia group; and group 3, diabetic group. Serum monocyte chemoattractant protein-1 levels before and after percutaneous coronary intervention (PCI), and the incidence of major adverse cardiovascular events 1-year post PCI were observed. The increase in monocyte chemoattractant protein-1 levels 24 h after percutaneous coronary intervention, compared with those before percutaneous coronary intervention, was significantly correlated with the blood glucose level at admission. Furthermore, the 1-year postoperative major adverse cardiovascular events rates were significantly higher in groups 2 and 3 compared with group 1. Logistic regression analysis demonstrated that a high blood glucose level at admission, diabetes, and high preoperative monocyte chemoattractant protein-1 levels were risk factors for major adverse cardiovascular events 1-year post-percutaneous coronary intervention. Stress hyperglycemia and diabetes may contribute to high monocyte chemoattractant protein-1 levels and prolonged inflammation. These symptoms are associated with poor prognosis of acute ST-segment elevation myocardial infarction in patients undergoing primary percutaneous coronary intervention.

Prognostic Value of the Acute-to-Chronic Glycemic Ratio at Admission in Acute Myocardial Infarction: A Prospective Study

OBJECTIVE

Acute hyperglycemia is a powerful predictor of poor prognosis in acute myocardial infarction (AMI), particularly in patients without diabetes. This emphasizes the importance of an acute glycemic rise rather than glycemia level at admission alone. We investigated in AMI whether the combined evaluation of acute and chronic glycemic levels, as compared with admission glycemia alone, may have a better prognostic value.

RESEARCH DESIGN AND METHODS

We prospectively measured admission glycemia and estimated average chronic glucose levels (mg/dL) by the following formula: [(28.7 × glycosylated hemoglobin %) - 46.7], and calculated the acute-to-chronic (A/C) glycemic ratio in 1,553 consecutive AMI patients (mean ± SD age 67 ± 13 years). The primary end point was the combination of in-hospital mortality, acute pulmonary edema, and cardiogenic shock.

RESULTS

The primary end point rate increased in parallel with A/C glycemic ratio tertiles (5%, 8%, and 20%, respectively; P for trend <0.0001). A parallel increase was observed in troponin I peak value (15 ± 34 ng/mL, 34 ± 66 ng/mL, and 68 ± 131 ng/mL; P < 0.0001). At multivariable analysis, A/C glycemic ratio remained an independent predictor of the primary end point and of troponin I peak value, even after adjustment for major confounders. At reclassification analyses, A/C glycemic ratio showed the best prognostic power in predicting the primary end point as compared with glycemia at admission in the entire population (net reclassification improvement 12% [95% CI 4-20]; P = 0.003) and, particularly, in patients with diabetes (27% [95% CI 14-40]; P < 0.0001).

CONCLUSIONS

In AMI patients with diabetes, A/C glycemic ratio is a better predictor of in-hospital morbidity and mortality than glycemia at admission.

Neuroendocrine System Regulatory Mechanisms: Acute Coronary Syndrome and Stress Hyperglycaemia

Neurohormonal systems are activated in the early phase of acute coronary syndromes to preserve circulatory homeostasis, but prolonged action of these stress hormones might be deleterious. Cortisol reaches its peak at 8 hours after the onset of symptoms, and individuals who have continued elevated levels present a worse prognosis. Catecholamines reach 100-1,000-fold their normal plasma concentration within 30 minutes of ischaemia, therefore inducing the propagation of myocardial damage. Stress hyperglycaemia induces inflammation and endothelial dysfunction, and also has procoagulant and prothrombotic effects. Patients with hyperglycaemia and no diabetes elevated in-hospital and 12-month mortality rates. Hyperglycaemia in patients without diabetes has been shown to be an appropriate independent mortality prognostic factor in this type of patient.

Stress Hyperglycemia and Prognosis of Minor Ischemic Stroke and Transient Ischemic Attack: The CHANCE Study (Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events)

BACKGROUND AND PURPOSE

We aimed to determine the association between stress hyperglycemia and risk of new stroke in patients with a minor ischemic stroke or transient ischemic attack.

METHODS

A subgroup of 3026 consecutive patients from 73 prespecified sites of the CHANCE trial (Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events) were analyzed. Stress hyperglycemia was measured by glucose/glycated albumin (GA) ratio. Glucose/GA ratio was calculated by fasting plasma glucose divided by GA and categorized into 4 even groups according to the quartiles. The primary outcome was a new stroke (ischemic or hemorrhagic) at 90 days. We assessed the association between glucose/GA ratio and risk of stroke by multivariable Cox regression models adjusted for potential covariates.

RESULTS

Among 3026 patients included, a total of 299 (9.9%) new stroke occurred at 3 months. Compared with patients with the lowest quartile, patients with the highest quartile of glucose/GA ratio was associated with an increased risk of stroke at 3 months after adjusted for potential covariates (12.0% versus 9.2%; adjusted hazard ratio, 1.46; 95% confidence interval, 1.06-2.01). Similar results were observed after further adjusted for fasting plasma glucose. We also observed that higher level of glucose/GA ratio was associated with an increased risk of stroke with a threshold of 0.29 using a Cox regression model with restricted cubic spline.

CONCLUSIONS

Stress hyperglycemia, measured by glucose/GA ratio, was associated with an increased risk of stroke in patients with a minor ischemic stroke or transient ischemic attack.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00979589.

Thrombosis in diabetes: a shear flow effect?

Cardiovascular events are the major cause of morbidity and mortality in Type 2 diabetes (T2D). This condition is associated with heightened platelet reactivity, contributing to increased atherothrombotic risk. Indeed, individuals with diabetes respond inadequately to standard antiplatelet therapy. Furthermore, they often experience recurrent events as well as side effects that include excess bleeding. This highlights the need for identification of novel regulators of diabetes-associated thrombosis to target for therapeutic intervention. It is well established that platelet aggregation, a process essential for thrombus formation, is tightly regulated by shear stress; however, the mechanisms underlying shear activation of platelets, particularly in the setting of diabetes, are still poorly understood. This review will address the limitations of current diagnostic systems to assess the importance of shear stress in the regulation of thrombus formation in T2D, and the inability to recapitulate the pro-thrombotic phenotype seen clinically in the setting of T2D. Moreover, we will discuss recent findings utilizing new technologies to define the importance of shear stress in thrombus formation and their potential application to the setting of diabetes. Finally, we will discuss the potential of targeting shear-dependent mechanisms of thrombus formation as a novel therapeutic approach in the setting of T2D.

Cardiac metabolism - A promising therapeutic target for heart failure

Both heart failure with reduced ejection fraction (HFrEF) and with preserved ejection fraction (HFpEF) are associated with high morbidity and mortality. Although many established pharmacological interventions exist for HFrEF, hospitalization and death rates remain high, and for those with HFpEF (approximately half of all heart failure patients), there are no effective therapies. Recently, the role of impaired cardiac energetic status in heart failure has gained increasing recognition with the identification of reduced capacity for both fatty acid and carbohydrate oxidation, impaired function of the electron transport chain, reduced capacity to transfer ATP to the cytosol, and inefficient utilization of the energy produced. These nodes in the genesis of cardiac energetic impairment provide potential therapeutic targets, and there is promising data from recent experimental and early-phase clinical studies evaluating modulators such as carnitine palmitoyltransferase 1 inhibitors, partial fatty acid oxidation inhibitors and mitochondrial-targeted antioxidants. Metabolic modulation may provide significant symptomatic and prognostic benefit for patients suffering from heart failure above and beyond guideline-directed therapy, but further clinical trials are needed.

New Developments in Platelet Cyclic Nucleotide Signalling: Therapeutic Implications

Altered platelet physiology may contribute to the emergence of thrombosis in patients with many forms of cardiovascular disease. Excess platelet activation may reflect increased stimulation of pro-aggregatory pathways. There is, however, increasing evidence that excessive platelet response, due to impaired efficacy of anti-aggregatory autacoids such as nitric oxide (NO) and prostacyclin (PGI₂), may be just as important. For example, diminished platelet response to NO has been documented in acute and chronic myocardial ischaemia, heart failure, aortic valve disease and in the presence of hyperglycaemia. This "NO resistance" has been shown to reflect both the scavenging of NO by reactive oxygen species and dysfunction of its intracellular "receptor", soluble guanylate cyclase. Importantly, these abnormalities of NO signalling are potentially reversible through judicious application of pharmacotherapy. The analogous condition of impaired PGI₂/adenylate cyclase (AC) signalling has received comparatively less attention to date. We have shown that platelet response to prostaglandin E₁ (PGE₁) is frequently impaired in patients with symptomatic myocardial ischaemia. Because the effects of ADP receptor antagonists such as clopidogrel and ticagrelor at the level of the P2Y₁₂ receptor are coupled with changes in activity of AC, impaired response to PGE₁ might imply both increased thrombotic risk and a reduced efficacy of anti-aggregatory drugs. Accordingly, patient response to treatment with clopidogrel is determined not only by variability of clopidogrel bio-activation, but also extensively by the integrity of platelet AC signalling. We here review these recent developments and their emerging therapeutic implications for thrombotic disorders.

The stress hyperglycemia ratio, an index of relative hyperglycemia, as a predictor of clinical outcomes after percutaneous coronary intervention

BACKGROUND

We aimed to investigate the outcome-predicting value of a novel index of stress hyperglycemia in coronary artery disease (CAD) patients who underwent percutaneous coronary intervention (PCI).

METHODS

This was a retrospective observational study. Four-thousand-three-hundred-sixty-two subjects from the COACT registry were used to estimate the risk of major adverse cardiovascular and cerebrovascular events (MACCE), which are defined as composites of all-cause death, non-fatal myocardial infarction (MI) and non-fatal stroke. The stress hyperglycemia ratio (SHR) was calculated by dividing the random serum glucose at admission with the estimated average glucose derived from HbA1c.

RESULTS

Over a median follow-up of 2.5years, 344 (7.9%), 43 (1.0%), and 89 (2.0%) cases of death, non-fatal MI, and non-fatal stroke occurred, respectively. Compared with the subjects in the lower three quartiles of SHR, the HR (95% CI) for the highest SHR quartile (Q4) group for MACCE was 1.31 (1.05, 1.64) in the total population and 1.45 (1.02, 2.06) in the non-diabetic population after adjusting for potential covariables. The risk of MACCE in the SHR Q4 group was significantly higher in patients presenting with ST-elevation MI (STEMI), which was not the case for patients presenting with other CAD types. The prognostic impact of SHR was more prominent for the 30-day MACCE. Similar results were observed in another cohort consisting of patients who only presented with acute MI.

CONCLUSIONS

SHR is a useful predictive marker of MACCE after PCI, especially in non-diabetic patients with STEMI, which could be utilized to identify high-risk patients for adverse outcomes.

The opposing roles of NO and oxidative stress in cardiovascular disease

Nitric oxide (NO) plays a pivotal role in the maintenance of cardiovascular homeostasis. A reduction in the bioavailability of endogenous NO, manifest as a decrease in the production and/or impaired signaling, is associated with many cardiovascular diseases including hypertension, atherosclerosis, stroke and heart failure. There is substantial evidence that reactive oxygen species (ROS), generated predominantly from NADPH oxidases (Nox), are responsible for the reduced NO bioavailability in vascular and cardiac pathologies. ROS can compromise NO function via a direct inactivation of NO, together with a reduction in NO synthesis and oxidation of its receptor, soluble guanylyl cyclase. Whilst nitrovasodilators are administered to compensate for the ROS-mediated loss in NO bioactivity, their clinical utility is limited due to the development of tolerance and resistance and systemic hypotension. Moreover, efforts to directly scavenge ROS with antioxidants has had limited clinical efficacy. This review outlines the therapeutic utility of NO-based therapeutics in cardiovascular diseases and describes the source and impact of ROS in these pathologies, with particular focus on the interaction with NO. Future therapeutic approaches in the treatment of cardiovascular diseases are highlighted with a focus on nitroxyl (HNO) donors as an alternative to traditional NO donors and the development of novel Nox inhibitors.

Emerging drugs for the treatment of angina pectoris

INTRODUCTION

Angina pectoris, or symptomatic myocardial ischaemia, reflects an impairment of coronary blood flow, and usually a deficiency of available myocardial energetics. Treatment options vary with the precise cause, which may vary with regards to the roles of increased myocardial oxygen demand versus reduced supply. Traditionally, organic nitrates, β-adrenoceptor antagonists, and non-dihydropyridine calcium antagonists were the only commonly used prophylactic anti-anginal agents. However, many patients failed to respond adequately to such therapy, and/or were unsuitable for their use. Areas covered: A number of 'new' agents have been shown to represent ancillary forms of prophylactic anti-anginal therapy and are particularly useful in patients who are relatively unsuitable for either percutaneous or surgical revascularisation. These include modulators of myocardial metabolic efficiency, such as perhexiline, trimetazidine and ranolazine, as well as high dose allopurinol, nicorandil and ivabradine. The advantages and disadvantages of these various agents are summarized. Expert opinion: 'Optimal' medical treatment of angina pectoris now includes use of agents primarily intended to reduce risk of infarction (e.g. statins, aspirin, ACE inhibitors). In patients whose angina persists despite the use of 'standard' anti-anginal therapy, and who are not ideal for invasive revascularization options, a number of emerging drugs offer prospects of symptomatic relief.

Gender and tachycardia: independent modulation of platelet reactivity in patients with atrial fibrillation

Background

Female patients with atrial fibrillation (AF) experience increased risk of thromboembolism compared to males, an observation that is reflected by its inclusion in the CHA₂DS₂VASc score. New onset AF (often associated with tachycardia) also confers upon patients increased thromboembolic risk. The mechanisms underlying this risk are uncertain, but new onset AF is associated with profound impairment of platelet nitric oxide (NO) signalling. Given that cardiovascular responses to catecholamines are gender-dependent, and that the presence of tachycardia in new onset AF may represent a response to catecholaminergic stimulation, we explored the potential impact of gender and tachycardia on platelet aggregation and NO signalling.

Methods

Interactions were sought in 87 AF patients between the extent of adenosine diphosphate (ADP)-induced platelet aggregation, the anti-aggregatory effects of the NO donor, sodium nitroprusside, gender, and admission heart rate. The potential impact of platelet expression of thioredoxin-interacting protein (Txnip) was also evaluated.

Results

Analysis of covariance confirmed the presence of physiological antagonism between platelet ADP and NO responses [F (1, 74) = 12.212, P < 0.01], while female sex correlated with impaired NO responses independent of platelet aggregability [F (2, 74) = 8.313, P < 0.01]. Admission heart rate correlated directly with platelet aggregation (r = 0.235, P < 0.05), and inversely with NO response (r = −0.331, P < 0.01). Txnip expression varied neither with gender nor with heart rate.

Conclusions

These results indicate that gender and heart rate are independent determinants of platelet function. Prospective studies of the putative benefit of reversal of tachycardia on restoration of normal platelet function are therefore a priority.

The relationship between fasting plasma glucose and MPO in patients with acute coronary syndrome

Background

Inflammation plays a critical role in the progression of atherosclerosis, and hyperglycemia is a common feature in patients with ACS. We investigated the relationship between fasting plasma glucose (FPG) levels and the levels of the inflammatory factor, myeloperoxidase (MPO), in patients with acute coronary syndrome (ACS).

Method

A total of 85 patients with no prior history of diabetes mellitus were recruited. The patients were divided into three groups based on their FPG levels as follows: group A, FPG < 5.6 mmol/l; group B, 5.6 mmol/l ≤ FPG < 6.1 mmol/l; and group C, FPG ≥ 6.1 mmol/l. The FPG concentrations and plasma MPO levels were determined, coronary angioplasty was performed, and the Gensini scores were used to evaluate the severity of the coronary lesion. The MPO expression in peripheral blood mononuclear cells (PBMCs) in patients with ACS was determined using western blot analysis.

Result

The results demonstrated that the levels of FPG were significantly and positively correlated with plasma MPO levels, Gensini scores, high sensitive C reaction protein(hs-CRP)levels, leukocyte and neutrophils count. In multivariate regression analyses the FPG levels were positively correlated with plasma MPO levels, Gensini score and hs-CRP. The plasma MPO levels in the group C [68.68(52.62–91.88) U/L] were significantly higher than in the group A [63.04(26.18–97.75) U/L] and group B [58.22(23.95–89.54) U/L]. The plasma hs-CRP concentrations are also higher in group C [42.28 (0.31–169.40) mg/L] than in the group A [12.51(0.28–176.25) mg/L] and group B [14.7 (0.14–89.68) mg/L].

Conclusion

This study demonstrates that FPG values are positively correlated with plasma MPO levels, suggesting MPO may play a role in the proatherogenesis of high FPG.

Hyperglycemia in acute coronary syndromes: from mechanisms to prognostic implications

Hyperglycemia is a frequent condition in patients with acute coronary syndromes (ACS). Hyperglycemia during ACS is caused by an inflammatory and adrenergic response to ischemic stress, when catecholamines are released and glycogenolysis induced. Although the involved pathophysiological mechanisms have not yet been fully elucidated, it is believed that hyperglycemia is associated with an increase in free fat acids (which induce cardiac arrhythmias), insulin resistance, chemical inactivation of nitric oxide and the production of oxygen reactive species (with consequent microvascular and endothelial dysfunction), a prothrombotic state, and vascular inflammation. It is also related to myocardial metabolic disorders, leading to thrombosis, extension of the damaged area, reduced collateral circulation, and ischemic preconditioning. In the last few years, several observational studies demonstrated that hyperglycemia in ACS is a powerful predictor of survival, increasing the risk of immediate and long-term complications in patients both with and without previously known diabetes mellitus. Glucose management strategies in ACS may improve outcomes in patients with hyperglycemia, perhaps by reducing inflammatory and clotting mediators, by improving endothelial function and fibrinolysis and by reducing infarct size. Recent clinical trials of insulin in ACS have resulted in varying levels of benefit, but the clinical benefit of an aggressive treatment with insulin is yet unproved.

Asymmetric dimethylarginine, a biomarker of cardiovascular complications in diabetes mellitus

Cardiovascular (CV) complications are an essential causal element of prospect in diabetes mellitus (DM), with carotid atherosclerosis being a common risk factor for prospective crisis of coronary artery diseases and/or cerebral infarction in DM subjects. From another point of view, asymmetric dimethylarginine (ADMA) has been established as an inhibitor of endogenous nitric oxide synthesis and the relationship between ADMA and arteriosclerosis has been reported. In our study with 87 type 2 DM (T2DM) patients, we have examined whether ADMA and other CV risk factors are the useful predictors of DMCV complications. After the measurement of the respective CV risk factors, we have followed the enrolled T2DM patients for 5 years. We have finally analyzed 77 patients. DMCV complications developed in 15 cases newly within 5 years, and 4 cases recurred. The concentrations of ADMA in plasma were markedly more elevated in 19 DM patients with CV complications than in 58 DM patients without CV complications. Urinary albumin (U-Alb), mean intimal-medial thickness (IMT) and ankle brachial index (ABI) were also higher in patients with CV complications. Multiple regression analyses showed that U-Alb had an influence on the high level of ADMA (standardized β = 6.59, P = 0.00014) independently of age, systolic BP, fibrinogen, mean IMT, plaque score, and ABI. The review indicates what is presently known regarding plasma ADMA that might be a new and meaningful biomarker of CV complications in DM subjects.

Meta-analysis of admission hyperglycaemia in acute myocardial infarction patients treated with primary angioplasty: a cause or a marker of mortality?

AIMS

Admission hyperglycaemia (AH) has been associated with worse outcomes in acute myocardial infarction (AMI). In the current review, we evaluated the impact of primary angioplasty (pPCI) on mortality in AMI patients with AH. Our second aim was to evaluate if AH is a marker of baseline risk or an independent predictor of mortality.

METHODS AND RESULTS

A comprehensive search of four major databases was performed. We included original research studies reporting data on mortality in AMI patients with AH (mean plasma glucose >156 mg/dL/8.7 mmol) and euglycaemia who were treated with pPCI. Of 481 citations, 12 studies were included in the analysis. Admission hyperglycaemia was associated with a higher 30-day [risk ratio (RR) 4.30, P < 0.0001] and 1- to 3-year mortality (RR 2.26, P < 0.0001). As well, AH was more prevalent in women and in patients with an increasing number of cardiac risk factors or angiographic predictors of mortality, such as previous AMI (RR 0.89, P = 0.01), multivessel coronary disease (RR 0.72, P = 0.0001), and involvement of left anterior descending artery (RR 0.92, P < 0.0001). Moreover, patients with AH had larger infarcts (higher creatine kinase-MB; P = 0.004) and more frequent ventricular arrhythmias (P = 0.002).

CONCLUSION

Despite rapid revascularization and treatment of hyperglycaemia, patients with AH continue to have a higher mortality. Admission hyperglycaemia occurs more commonly in patients who have traditional predictors of worse outcomes-specifically prior infarction, anterior wall infarctions, and multivessel disease. Likely, AH is a predictor of rather than a bona fide therapeutic target in AMI.

Thioredoxin-interacting protein: pathophysiology and emerging pharmacotherapeutics in cardiovascular disease and diabetes

The thioredoxin system, which consists of thioredoxin (Trx), nicotinamide adenine dinucleotide phosphate (NADPH) and thioredoxin reductase (TrxR), has emerged as a major anti-oxidant involved in the maintenance of cellular physiology and survival. Dysregulation in this system has been associated with metabolic, cardiovascular, and malignant disorders. Thioredoxin-interacting protein (TXNIP), also known as vitamin D-upregulated protein or thioredoxin-binding-protein-2, functions as a physiological inhibitor of Trx, and pathological suppression of Trx by TXNIP has been demonstrated in diabetes and cardiovascular diseases. Furthermore, TXNIP effects are partially Trx-independent; these include direct activation of inflammation and inhibition of glucose uptake. Many of the effects of TXNIP are initiated by its dissociation from intra-nuclear binding with Trx or other SH-containing proteins: these effects include its migration to cytoplasm, modulating stress responses in mitochondria and endoplasmic reticulum, and also potentially activating apoptotic pathways. TXNIP also interacts with the nitric oxide (NO) signaling system, with apparent suppression of NO effect. TXNIP production is modulated by redox stress, glucose levels, hypoxia and several inflammatory activators. In recent studies, it has been shown that therapeutic agents including insulin, metformin, angiotensin converting enzyme inhibitors and calcium channel blockers reduce TXNIP expression, although it is uncertain to what extent TXNIP suppression contributes to their clinical efficacy. This review addresses the role of TXNIP in health and in cardiovascular and metabolic disorders. Finally, the potential advantages (and disadvantages) of pharmacological suppression of TXNIP in cardiovascular disease and diabetes are summarized.

Hypoxic potentiation of nitrite effects in human vessels and platelets

Previous studies in non-human blood vessels and in platelets have demonstrated that under hypoxic conditions release of NO from nitrite (NO2(-)) is potentiated by deoxyhaemoglobin. In the current study, we characterized hypoxic potentiation of NO2(-) effects in human vasculature and platelets in vitro, addressing underlying mechanisms. The vasodilator efficacy of NO2(-), in comparison with glyceryl trinitrate (GTN), was evaluated in vitro, using segments of human saphenous vein. Under hypoxic conditions, there was a leftward shift of the NO2(-) concentration-response curve (EC50: 22 μM in hyperoxia vs 3.5 μM in hypoxia; p<0.01), but no significant potentiation of GTN effect. In the presence of red blood cells, hypoxic potentiation of NO2(-) vasodilator effect was accentuated. In whole blood samples and platelet-rich plasma (PRP) we assessed inhibition of platelet aggregation by NO2(-) (1mM), in comparison with that of sodium nitroprusside (SNP, 10 μM). In individual subjects (n=37), there was a strong correlation (r=0.75, p<0.0001) between anti-aggregatory effects of NO2(-) and SNP in whole blood, signifying that resultant sGC activation underlies biological effect and responses to NO2(-) are diminished in the presence of NO resistance. In PRP, the effects of NO2(-) were less pronounced than in whole blood (p=0.0001), suggesting an important role of Hb (within RBCs) in the bioconversion of NO2(-) to NO. Inhibition of platelet aggregation by NO2(-) was almost 3-fold greater in venous than in arterial blood (p<0.0001), and deoxyHb concentration directly correlated (r=0.69, p=0.013) with anti-aggregatory response. Incremental hypoxia applied to venous blood samples (in hypoxic chamber) caused a progressive increase in both deoxyHb level and anti-aggregatory effect of NO2(-). When subjects inhaled a 12% O2 mixture for 20 min, there was a 3-fold rise in blood deoxyHb fraction (p<0.01). In PRP, response to NO2(-) also increased under hypoxia, and was further enhanced (p<0.01) by deoxyHb. Furthermore, deoxyHb exerted significant anti-aggregatory effects even in the absence of added NO2(-), suggesting a role for endogenous NO2(-). The results of this work provide further mechanistic insights into hypoxic potentiation of vasodilator and anti-aggregatory actions of NO2(-). In human saphenous veins and blood, the balance of evidence suggests differential rates of NO release from NO2(-) (largely modulated by deoxyHb) as the fundamental mechanism.

Cardiomyocyte glycophagy is regulated by insulin and exposure to high extracellular glucose

Disturbed systemic glycemic and insulinemic status elicits cardiomyocyte metabolic stress and altered glucose handling. In diabetes, pathological myocardial glycogen accumulation occurs. Recently, evidence of a specific myocardial autophagic degradation pathway for glycogen ("glycophagy") has been reported, differentiated from the more well-characterized protein "macrophagy" pathway. The goal of this study was to identify potential mechanisms involved in cardiac glycogen accumulation, glycophagy, and macrophagy regulation using cultured neonatal rat ventricular myocytes (NRVMs). In NRVMs, insulin-induced Akt phosphorylation was evident with 5 mM-glucose conditions (∼2.3-fold increased). Under high-glucose (30 mM) conditions, insulin-augmented phosphorylation was not observed. Accumulation of glycogen was observed in response to insulin only in high-glucose conditions (∼2-fold increase). Increased expression of the glycophagy marker starch-binding domain-containing protein-1 (STBD1, 25% increase) was observed under high-glucose and insulin conditions. Expression levels of the macrophagy markers p62 and light chain protein 3BII:I were not increased by insulin at either glucose level. Preliminary results from hearts of streptozotocin-treated diabetic rats are supportive of the findings obtained in NRVMs, suggesting diabetes induced elevated expression of STBD1 and of an additional glycophagy marker GABA(A) receptor-associated protein-like 1. Confocal microscopy demonstrated that light chain protein 3B and STBD1 immunomarkers were not colocalized in NRVMs. These findings provide the first evidence that cardiomyocyte glycophagy induction occurs under the influence of insulin and is responsive to extracellular high glucose. This study suggests that the regulation of glycogen content and glycophagy induction in the cardiomyocyte may be linked, and it is speculated that glycogen pathology in diabetic cardiomyopathy has glycophagic involvement.

Prediabetes and short-term outcomes in nondiabetic patients after acute ST-elevation myocardial infarction

OBJECTIVES

A prediabetic state is defined as the time period before the development of symptomatic diabetes. Limited evidence is available for evaluating the correlation between prediabetes and short-term outcomes in nondiabetic patients with ST-elevation of myocardial infarction (STEMI).

METHODS

4,787 nondiabetic patients with a diagnosis of STEMI based on typical onset of chest pain within 12 h were enrolled. Patients were followed up for 7 and 30 days after hospital admission. According to the 2013 Standards of Medical Care in Diabetes, the study population was stratified into three groups: normal, prediabetic and newly diagnosed diabetic patients. The primary outcomes of our study were all-cause mortality and major adverse cardiac events (MACE) on days 7 day and 30.

RESULTS

The proportions of patients with prediabetes and newly diagnosed diabetes were 31.1 and 19.2%, respectively. Rates of 7- and 30-day mortality and MACE were similar among the different HbA1c groups. Multivariable Cox regression analysis showed that compared with normal glucose metabolism, prediabetes (hazard ratio, HR, 1.003; 95% CI, 0.865-1.165) and newly diagnosed diabetes (HR, 0.887; 95% CI, 0.739-1.064) were not correlated with 30-day MACE. However, admission glucose was an independent predictor of short-term MACE (HR, 1.031; 95% CI, 1.017-1.046).

CONCLUSIONS

In nondiabetic patients after STEMI, the incidence of latent diabetes mellitus was increased. Newly diagnosed diabetes and prediabetes were not correlated with short-term outcome in nondiabetic patients with STEMI, yet admission glucose level was an independent predictor of short-term MACE. To reduce the incidence of short-term MACE after STEMI, more attention should be paid to the control of increased glucose levels and intrinsic stress states.

Risk of cardiovascular diseases in diabetes mellitus and serum concentration of asymmetrical dimethylarginine

Introduction. Asymmetric dimethylarginine (ADMA) is a nonselective nitric oxide (NO) synthase inhibitor associated with cardiovascular and metabolic disorders. ADMA plays an important role in the regulation of vascular tone by acting as an endogenous inhibitor of NO synthesis. Objectives. This study aimed to investigate ADMA with respect to diabetes and its clinical relevance as an independent predictor of CAD (Coronary Artery Disease). Methodology. The present case control study includes two hundred and forty patients selected randomly. Serum ADMA was analyzed by using enzyme immunoassay for the quantitative determination of endogenous ADMA, and serum nitric oxide was estimated by the method of Cortes. Results. Elevated NO level levels was a strong predictor and significantly (t: 9.86, P < 0.001) associated with occurrence of CAD. Increased ADMA level was found to be another strong predictor and associated significantly (t: 8.02, P < 0.001) with CAD. On intra group analysis, the relationship between ADMA and NO in diseased group, is significant negative correlation (r = -0.743). P (0.001) was found between ADMA and NO. Conclusion. ADMA level was found to be one of the strong predictors for CAD. ADMA is an emerging independent risk marker for future CVD (cardiovascular disease) events.

The nitric oxide redox sibling nitroxyl partially circumvents impairment of platelet nitric oxide responsiveness

Impaired platelet responsiveness to nitric oxide (NO resistance) is a common characteristic of many cardiovascular disease states and represents an independent risk factor for cardiac events and mortality. NO resistance reflects both scavenging of NO by superoxide (O2(-)), and impairment of the NO receptor, soluble guanylate cyclase (sGC). There is thus an urgent need for circumvention of NO resistance in order to improve clinical outcomes. Nitroxyl (HNO), like NO, produces vasodilator and anti-aggregatory effects, largely via sGC activation, but is not inactivated by O2(-). We tested the hypothesis that HNO circumvents NO resistance in human platelets. In 57 subjects with or without ischemic heart disease, platelet responses to the HNO donor isopropylamine NONOate (IPA/NO) and the NO donor sodium nitroprusside (SNP) were compared. While SNP (10μM) induced 29±3% (p<0.001) inhibition of platelet aggregation, IPA/NO (10μM) caused 75±4% inhibition (p<0.001). In NO-resistant subjects (n=28), the IPA/NO:SNP response ratio was markedly increased (p<0.01), consistent with partial circumvention of NO resistance. Similarly, cGMP accumulation in platelets was greater (p<0.001) with IPA/NO than with SNP stimulation. The NO scavenger carboxy-PTIO (CPTIO, 200μM) inhibited SNP and IPA/NO responses by 92±7% and 17±4% respectively (p<0.001 for differential inhibition), suggesting that effects of IPA/NO are only partially NO-mediated. ODQ (10μM) inhibited IPA/NO responses by 36±8% (p<0.001), consistent with a contribution of sGC/haem to IPA/NO inhibition of aggregation. There was no significant relationship between whole blood ROS content and IPA/NO responses. Thus the HNO donor IPA/NO substantially circumvents platelet NO resistance while acting, at least partially, as a haem-mediated sGC activator.

Reciprocal regulation of NO signaling and TXNIP expression in humans: impact of aging and ramipril therapy

BACKGROUND

Impaired tissue responsiveness to nitric oxide (NO) occurs in many cardiovascular diseases as well as with advanced age and is a correlate of poor outcomes. This phenomenon results from oxidative stress, with NO "scavenging" and dysfunction of soluble guanylate cyclase (sGC). Thioredoxin-interacting protein (TXNIP) is a major intracellular regulator of inflammatory activation and redox stress, but its interactions with NO/sGC are poorly understood. We have now evaluated the relationship between platelet TXNIP expression and function of the NO/sGC axis in subjects of varying age and during therapy with ramipril.

METHODS & RESULTS

Young (n=42) and aging (n=49) subjects underwent evaluation of platelet TXNIP content. Aging subjects additionally had measurements of platelet NO responsiveness and routine biochemistry. Platelet TXNIP content was greater (376±33 units) in the aging compared to younger subjects (289±13 units; p<0.05). In the aging subjects there was a significant negative correlation (r=-0.50, p<0.001) between platelet TXNIP content and NO responsiveness. In a separate cohort of 15 subjects two week treatment with ramipril, which reversed platelet NO resistance and potentiated sGC activity, also decreased platelet TXNIP content by 40% (p=0.011).

CONCLUSIONS

Platelet TXNIP content increases with aging, varies inversely with responsiveness to NO, and diminishes rapidly following treatment with ramipril. These data suggest that TXNIP-induced oxidative stress may be a critical modulator of tissue resistance to NO, a fundamental basis for cardiovascular disease. Analogously suppression of TXNIP expression can potentially be utilized as an index of restoration of cardiovascular homeostasis.

Examining the role of insulin in the regulation of cardiovascular health

A substantial body of evidence has reported that insulin has direct actions on the cardiovascular system independent of its systemic effects on plasma glucose or lipids. In particular, insulin regulates endothelial synthesis of the vasoactive mediators nitric oxide and endothelin-1, yet the importance of this in the maintenance of cardiovascular health remains poorly understood. Recent studies using animals with targeted downregulation of insulin signaling in vascular tissues are improving our understanding of the role of insulin in vascular health. This article focuses on the direct actions of insulin in cardiovascular tissues, with particular emphasis on the molecular mechanisms of insulin action on endothelial function. The potential contribution of impaired vascular insulin action to the cardiovascular complications of diabetes will also be discussed.

Cardiovascular benefits of exogenous insulin

CONTEXT

Recent studies on mediators of inflammation, experimental models of atherosclerosis, and acute ischemia have identified novel mechanisms through which insulin may exert cardiovascular protective effects. This review aims to summarize current knowledge regarding the cardiovascular, antiinflammatory, and antiatherogenic effects of insulin, and the effect of intensive glycemic control in acute cardiovascular disease.

EVIDENCE ACQUISITION

Publications of interest were identified using preselected MeSH terminology and keywords to search online databases such as PubMed and OVID for the period January 1988 to February 2012. Relevant publications were obtained and reviewed by two independent observers, then evaluated a priori against the following criteria: study quality, main clinical outcomes, and applicability to clinical practice.

EVIDENCE SYNTHESIS

Insulin has been shown to exert vasodilatory, antiinflammatory, and antiatherogenic effects in experimental models, independent of its glucose-lowering effects. Additionally, glucose is known to exert potent proinflammatory, prothrombotic, and proapoptotic effects during myocardial infarct, indicative that hyperglycemia is likely to be injurious to the heart. In this context, through its nonmetabolic and metabolic (glucose-lowering) effects, insulin is likely to be cardioprotective and to improve clinical outcomes in acute myocardial infarction.

CONCLUSIONS

Despite promising experimental data and evidence of benefit from single-center randomized clinical trials, clinical evidence supporting the cardioprotective effects of insulin from a multicenter randomized clinical trial is still lacking. Future prospective studies with insulin infused at adequate concentrations, individually titrated to achieve and maintain euglycemia (blood glucose < 140 mg/dl) and minimize hypoglycemia, are required to investigate the role of insulin in the management of patients with acute cardiovascular disease.

Ramipril sensitizes platelets to nitric oxide: implications for therapy in high-risk patients

OBJECTIVES

Using 2 sequential studies in HOPE (Heart Outcomes Prevention Evaluation) study-type patients, the aims of this study were: 1) to test the hypothesis that ramipril improves platelet nitric oxide (NO) responsiveness: and 2) to explore biochemical and physiological effects of ramipril in a cohort selected on the basis of platelet NO resistance.

BACKGROUND

Ramipril prevents cardiovascular events, but the bases for these effects remain uncertain. NO resistance at both the platelet and vascular levels is present in a substantial proportion of patients with diabetes or ischemic heart disease and is an independent risk factor for cardiovascular events.

METHODS

Study 1 was a double-blind, randomized comparison of ramipril (10 mg) with placebo in a cohort of patients (n = 119) with ischemic heart disease or diabetes plus additional coronary risk factor(s), in which effects on platelet responsiveness to NO were compared. Study 2 was a subsequent short-term evaluation of the effects of ramipril in a cohort of subjects (n = 19) with impaired platelet NO responsiveness in whom additional mechanistic data were sought.

RESULTS

In study 1, ramipril therapy increased platelet responsiveness to NO relative to the extent of aggregation (p < 0.001), but this effect occurred primarily in patients with severely impaired baseline NO responsiveness (n = 41). In study 2, ramipril also improved platelet NO responsiveness (p < 0.01), and this improvement was correlated directly with increased NO-stimulated platelet generation of cyclic guanosine monophosphate (p < 0.02) but not with changes in plasma thrombospondin-1 levels.

CONCLUSIONS

Ramipril ameliorates platelet NO resistance in HOPE study-type patients, with associated increases in soluble guanylate cyclase responsiveness to NO. This effect is likely to contribute to treatment benefit and define patients in whom ramipril therapy is particularly effective.

Role of the PPAR-α agonist fenofibrate in severe pediatric burn

Fenofibrate is a peroxisome proliferator activated receptor alpha agonist that contains both pro and anti-inflammatory properties, and has been used in the treatment of dyslipidemia and diabetes for decades. Its receptors are expressed in the liver, skeletal muscle, cardiac, enteric, and renal cells, which allow it to provide systemic regulation of lipoprotein metabolism, fatty acid oxidation, and fatty acid transport. Hyperglycemia is a common complication found in the burn population because hepatic glucose production and catecholamine-mediated hepatic glycogenolysis are augmented. Insulin resistance occurs often in these patients and is associated with poor outcomes. In the pediatric burn population, fenofibrate has been found to ameliorate or decrease the number of hypoglycemic episodes when compared to management with insulin alone. Its mechanism of action is thought to involve an improvement in insulin signaling in skeletal muscle, as well as improvements in mitochondrial function, glucose oxidation, and insulin sensitivity. The long term use of fenofibrate in severely burned patients may improve hyperglycemia and insulin resistance, as well as improve wound healing, and reduce apoptosis, and oxidative stress.

Clinical significance of hyperglycaemia in acute coronary syndrome patients

BACKGROUND

The clinical significance of moment measurements (admission and fasting glycaemia), persistent (hyperglycaemic index, HGI; time average glucose, TAG; mean glucose; maximum glucose) or chronic hyperglycaemia (HbA1c), estimated average glucose, eAG) is still elusive in clinical practice.

AIM

To identify the clinical significance of hyperglycaemia in ACS.

METHODS

The study included 226 consecutive patients with ACS. Indicators for hyperglycaemia were defined, calculated and a correlation analysis with standard parameters-EF, maximum CPK, maximum CPK-MB and troponin was performed. Patients were followed up for 12 months.

RESULTS

Indicators for persistent and chronic hyperglycaemia correlated neither to ejection fraction, nor to the enzymes for myocardial necrosis (P > 0.05). In contrast, acute hyperglycaemia correlated negatively with ventricular systolic dysfunction (P = 0.001/0.007) and positively with maximum CPK, MB and troponin (P = 0.0001/0.008). TAG was an independent predictor for 6-month re-hospitalization (P = 0.027) because of cardiac complications.

CONCLUSION

Glycaemia at admission and fasting glucose could be used as metabolic surrogate markers for ventricular systolic dysfunction and TAG as an independent surrogate marker for six-month re-hospitalization. None of the indicators for hyperglycaemia could be used as independent prognostic factors for survival. Hyperglycaemia rather reflects an underlying impairment in glucose metabolism.

Impact of hyperglycemia at admission in patients with acute ST-segment elevation myocardial infarction as assessed by contrast-enhanced MRI

BACKGROUND

Blood glucose level at admission in ST-segment elevation myocardial infarction (STEMI) is a predictor of heart failure and mortality. This study was performed to investigate the impact of hyperglycemia at admission in non-diabetic patients on infarct size, microvascular obstruction, and long-term outcome using contrast-enhanced magnetic resonance imaging (CMR) in patients with acute STEMI.

METHODS

One hundred and seven consecutive patients (84 males; mean age 59.4 years ± 11.3 years) with a first acute STEMI successfully treated by primary PCI were included. Admission hyperglycemia was defined as blood glucose above 7.8 mmol/l. CMR was performed 3.6 days ± 1.9 days after admission on a 1.5-tesla MR system. The imaging protocol included single-shot steady-state free precession (SSFP) cine sequences for assessing segmental and global left ventricular (LV) function and microvascular obstruction (MVO)/late gadolinium enhancement (LGE) imaging immediately and 10 min after the administration of 0.2 mmol gadodiamide/kg of body weight using an inversion-recovery SSFP (IR-SSFP) sequence. A receiver operating characteristics analysis was used to detect the best cut-off point of microvascular obstruction that predicted myocardial infarction and death during follow-up.

RESULTS

Of 107 patients, 37 (35%) had hyperglycemia on admission. Compared to normoglycemic patients, patients with admission hyperglycemia had a lower LV ejection fraction (38.6 ± 13.7% vs. 47.5 ± 12.2%, p < 0.001), greater ESV (88.8 ± 41.8 ml vs. 72.3 ml ± 35.1 ml, p = 0.01), greater infarct size (LGE% 21.1 ± 14.9% vs. 9.8 ± 8.7%, p < 0.001), and greater MVO (MVO% 9.6 ± 9.9% vs. 2.5 ± 4.3%, p < 0.001). Admission hyperglycemia was an independent predictor of the presence and extent of microvascular obstruction. Microvascular obstruction as a percentage of left ventricular mass was the only variable independently related to clinical outcome in a Cox proportional hazard model (Wald 18.78, HR 1.155, p < 0.001).

CONCLUSION

Hyperglycemia at admission in STEMI patients who are successfully treated by PCI is independently associated with the presence and extent of microvascular obstruction on contrast-enhanced CMR. Thus, microvascular obstruction as assessed by CMR may be a mechanism that relates admission hyperglycemia in acute STEMI to worse outcome.

Admission glucose level and in-hospital outcomes in diabetic and non-diabetic patients with ST-elevation acute myocardial infarction

BACKGROUND

Hyperglycemia on admission is a predictor of an unfavorable prognosis in patients with ST-elevation Acute Myocardial Infarction (AMI). Data concerning associations between an elevated glucose level on admission and other in-hospital complications are still limited.

METHODS

A total of 1,137 AMI patients with complete admission blood glucose level (ABGL) analysis were identified and stratified according to ABGL.

RESULTS

A total of 16.1% patients had admission glucose level <5 mmol/L, 36.1% <7 mmol/L, 20.2% <9 mmol/L, 9.9% <11 mmol/L and 17.7% ≥11 mmol/L. Compared with the euglycemia group, both the hypo- and hyperglycemia groups were associated with higher in-hospital mortality. In-hospital mortality of diabetic patients with hypoglycemia (12.2%) was higher than that of diabetic patients with either euglycemia or mild hyperglycemia (11.1%, or 10.7% relatively). The same results were seen in non-diabetic patients. In the logistic regression analysis, admission glucose and cardiac function of Killip grade were the independent predictors of in-hospital death for patients with AMI.

CONCLUSION

Elevated admission glucose levels are associated with an increased risk of life-threatening complications in diabetic and non-diabetic AMI patients. Compared with the euglycemia group, hypoglycemia was associated with a higher trend of in-hospital mortality.

Acute hyperglycemia and contrast-induced nephropathy in primary percutaneous coronary intervention

BACKGROUND

Acute hyperglycemia and contrast-induced nephropathy (CIN) are frequently observed in ST-elevation acute myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI), and both are associated with an increased mortality rate. We investigated the possible association between acute hyperglycemia and CIN in patients undergoing primary PCI.

METHODS

We prospectively enrolled 780 STEMI patients undergoing primary PCI. For each patient, plasma glucose levels were assessed at hospital admission. Acute hyperglycemia was defined as glucose levels>198 mg/dL (11 mmol/L). Contrast-induced nephropathy was defined as an increase in serum creatinine>25% from baseline in the first 72 hours.

RESULTS

Overall, 148 (19%) patients had acute hyperglycemia; and 113 (14.5%) patients developed CIN. Patients with acute hyperglycemia had a 2-fold higher incidence of CIN than those without acute hyperglycemia (27% vs 12%, P<.001). In-hospital mortality was higher in patients with acute hyperglycemia than in those without acute hyperglycemia (12% vs 3%, P<.001). Mortality rate was also higher in patients developing CIN than in those without this renal complication (27% vs 0.9%, P<.001). Patients with acute hyperglycemia that developed CIN had the highest mortality rate (38%). Acute hyperglycemia was an independent predictor of CIN and in-hospital mortality.

CONCLUSIONS

In STEMI patients undergoing primary PCI, acute hyperglycemia is associated with an increased risk for CIN and with increased in-hospital mortality.

Hyperglycemia on admission predicts larger infarct size in patients undergoing percutaneous coronary intervention for acute ST-segment elevation myocardial infarction

AIMS

To determine if hyperglycemia on admission correlates to infarct size measured by single-photon emission computed tomography (SPECT) in patients with acute ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI).

METHODS

We evaluated 347 STEMI patients who underwent primary PCI. Infarct size was determined by SPECT on Day 5. The population was divided into: hyperglycemia (glycemia on admission >11mmol/L) or non-hyperglycemia (<or=11mmol/L) regardless of diabetic status.

RESULTS

61 (17.6%) patients presented with hyperglycemia on admission. There were no significant differences in baseline characteristics or in PCI characteristics between the two groups. Final TIMI 3 flow was achieved in 81.7% of patients with hyperglycemia vs 85.7% of patients with non-hyperglycemia (p=0.43). The infarct size was larger in the hyperglycemia group (6 [2-14]% vs 8.5 [3-18.25]%; p=0.016). A multivariate linear regression analysis showed that hyperglycemia on admission was an independent predictor of infarct size at Day 5 post-MI (p=0.004).

CONCLUSION

In patients with STEMI treated with primary PCI, hyperglycemia on admission is associated with larger infarct size determined by SPECT.

Detrimental effects of energy drink consumption on platelet and endothelial function

BACKGROUND

Energy drink consumption has been anecdotally linked with sudden cardiac death and, more recently, myocardial infarction. As myocardial infarction is strongly associated with both platelet and endothelial dysfunction, we tested the hypothesis that energy drink consumption alters platelet and endothelial function.

METHODS

Fifty healthy volunteers (34 male, aged 22+/-2 years) participated in the study. Platelet aggregation and endothelial function were tested before, and 1 hour after, the consumption of 250 mL (1 can) of a sugar-free energy drink. Platelet function was assessed by adenosine diphosphate-induced (1 micromol/L) optical aggregometry in platelet-rich plasma. Endothelial function was assessed via changes in peripheral arterial tonometry and expressed as the reactive hyperemia index (RHI).

RESULTS

Compared with baseline values, there was a significant increase in platelet aggregation following energy drink consumption, while no change was observed with control (13.7+/-3.7% vs 0.3+/-0.8% aggregation, respectively, P <.01). Similarly, RHI decreased following energy drink consumption (-0.33+/-0.13 vs 0.07+/-0.12 RHI [control], P <.05). Mean arterial pressure significantly increased following energy drink consumption, compared with control (P <.05). Heart rate was unaffected by energy drink consumption.

CONCLUSION

Energy drink consumption acutely increases platelet aggregation and decreases endothelial function in healthy young adults.

Comparison of blood glucose values on admission for acute myocardial infarction in patients with versus without diabetes mellitus

Previous studies have reported that acute hyperglycemia is associated with high mortality after acute myocardial infarction (AMI). However, optimal plasma glucose level may be different between diabetic and nondiabetic patients. The purpose of this study was to assess the relation between admission glucose and in-hospital mortality after AMI in patients with and without diabetes. This study consisted of 3,750 patients who were admitted to the 35 hospitals participating to the Japanese Acute Coronary Syndrome Study (JACSS) group within 48 hours after the onset of AMI. Plasma glucose was measured at the time of hospital admission. In patients without a history of diabetes, there was a linear relation between admission glucose and in-hospital mortality. Nondiabetic patients with a glucose level <6 mmol/L had the lowest mortality (2.5%). As admission glucose increased by 1 mmol/L, mortality increased by 17% (13% to 21%, p <0.001). In patients with a history of diabetes, however, there was a U-shape relation between glucose and mortality. Diabetic patients with glucose 9 to 10 mmol/L had the lowest mortality (1.9%); not only severe hyperglycemia (glucose > or =11 mmol/L, 9.1%, p <0.001) but also euglycemia (glucose <7 mmol/L, 9.4%, p = 0.009) were associated with higher mortality compared to moderate hyperglycemia (glucose 9 to 11 mmol/L, 3.2%). Diabetic patients with admission glucose 9 to 10 mmol/L had the lowest mortality, whereas lower glucose was better in nondiabetic patients. In conclusion, optimal glucose level on admission may be different between diabetic and nondiabetic patients with AMI.

Exploiting cGMP-based therapies for the prevention of left ventricular hypertrophy: NO* and beyond

Left ventricular hypertrophy (LVH), an increased left ventricular (LV) mass, is common to many cardiovascular disorders, initially developing as an adaptive response to maintain myocardial function. In the longer term, this LV remodelling becomes maladaptive, with progressive decline in LV contractility and diastolic function. Indeed LVH is recognised as an important blood-pressure independent predictor of cardiovascular morbidity and mortality. The clinical efficacy of current treatments for LVH is reduced, however, by their tendency to slow disease progression rather than induce its reversal, and thus the development of new therapies for LVH is paramount. The signalling molecule cyclic guanosine-3',5'-monophosphate (cGMP), well-recognised for its role in regulating vascular tone, is now being increasingly identified as an important anti-hypertrophic mediator. This review is focused on the various means by which cGMP can be stimulated in the heart, such as via the natriuretic peptides, to exert anti-hypertrophic actions. In particular we address the limitations of traditional nitric oxide (NO*) donors in the face of the potential therapeutic advantages offered by novel alternatives; NO* siblings, ligands of the cGMP-generating enzymes, soluble (sGC) and particulate guanylyl cyclases (pGC), and phosphodiesterase inhibitors. Further impact of cGMP within the cardiovascular system is also discussed with a view to representing cGMP-based therapies as innovative pharmacotherapy, alone or concurrent with standard care, for the management of LVH.

Insulin as an anti-inflammatory and antiatherogenic modulator

Data demonstrate the anti-inflammatory effects of insulin and proinflammatory effects of glucose. These data provide a mechanistic justification for the benefits of maintaining euglycemia with insulin infusions in hospitalized patients. Regimens that infuse fixed doses of insulin with high rates of glucose are usually associated with hyperglycemia, which may neutralize the beneficial effects of insulin. Therefore, we propose that such regimens should be avoided and instead replaced by insulin infusions that normalize and maintain blood glucose at a reasonably low level and ensure that plasma insulin is maintained at levels high enough to provide clinically relevant anti-inflammatory and cardioprotective effects. Trials to test this hypothesis are in progress.

ADMA, cardiovascular disease and diabetes

The endogenous competitive nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) is an emerging risk marker for future cardiovascular events. Elevated ADMA concentrations have been described in patients with an adverse cardiovascular risk profile. Recently, various studies investigated the independent role of ADMA as a cardiovascular risk predictor in several patient cohorts. In addition, ADMA might not only be a risk marker but also a causative factor for cardiovascular disease. This review summarizes the literature on the relationship between ADMA, cardiovascular disease and diabetes.

Oral glyburide, but not glimepiride, blocks the infarct-size limiting effects of pioglitazone

BACKGROUND

Many patients with type 2 diabetes mellitus receive several oral hypoglycemic agents, including sulfonylurea drugs. Intravenous glyburide (Glyb), a sulfonylurea agent, blocks the protective effects of "ischemic" and pharmacologic preconditioning in various animal models without affecting myocardial infarct size when administered alone. However, there are conflicting results when other sulfonylurea drugs are used. Pioglitazone (PIO) reduces infarct size in the rat. We asked whether oral Glyb and glimepiride (Glim) affect the infarct size-limiting effects of PIO.

METHODS

Sprague-Dawley rats received 3-day oral treatment with: PIO (5 mg/kg/day); PIO + Glyb (10 mg/kg/day); PIO + Glim (4 mg/kg/day) or water alone (experiment 1) or PIO (5 mg/kg/day) with or without 5-hydroxydecanoate (5HD, 10 mg/kg), a specific mitochondrial ATP-sensitive K+ channels inhibitor, administered intravenously 30 min before coronary artery ligation. PIO, Glyb and Glim were administered by oral gavage. Sugar 5% was added to water to prevent hypoglycemia. Rats underwent 30 min coronary artery occlusion and 4 h reperfusion (n = 6 in each group). Ischemic area at risk was assessed by blue dye and infarct size by triphenyl-tetrazolium-chloride.

RESULTS

Body weight and the size of the area at risk were comparable among groups. Infarct size (% of the area at risk) was significantly smaller in the PIO (14.3 +/- 1.1%; p < 0.001) and PIO + Glim (13.2 +/- 0.8%; p < 0.001) groups than in the control group (37.7 +/- 1.2%). Glyb completely blocked the effect of PIO (43.0 +/- 1.7%; p < 0.001). Glim did not affect the protective effect of PIO (p = 0.993). 5HD blocked the protective effect of PIO (infarct size 48.5 +/- 0.8% versus 14.8 +/- 0.6%, respectively; p < 0.0001). In conclusion, the infarct size limiting effects of PIO are dependent on activation of mitochondrial ATP-sensitive K+ channels. Oral Glyb, but not Glim, blocks the infarct size limiting effects of PIO. It is plausible that Glyb affects other pleiotropic effects of PIO and thus may attenuate favorable effects on cardiovascular outcomes. In contrast, Glim does not attenuate the protective effect of PIO.

Polycystic ovary syndrome is associated with severe platelet and endothelial dysfunction in both obese and lean subjects

Platelet hyporesponsiveness to the anti-aggregatory effects of nitric oxide (NO) occurs commonly in association with myocardial ischemia and coronary risk factors, often co-exists with endothelial dysfunction and represents an independent marker of long-term cardiovascular risk. We sought to determine whether polycystic ovary syndrome (PCOS), which has been postulated as a cardiovascular risk factor in women, is independently associated with this phenomenon. Twenty-four young women with PCOS (mean age 32.1+/-1.3) were evaluated in lean (n=12) and obese (n=12) subgroups, and compared with age-matched lean normals (n=12). Platelet aggregation and its inhibition by the nitric oxide donor sodium nitroprusside (SNP) were assessed and compared with vascular endothelial function. Plasma concentrations of malondialdehyde (MDA), N(G),N(G)-dimethyl-L-arginine (ADMA) and hs-CRP were measured as markers of oxidative stress, endothelial dysfunction and inflammation, respectively. Circulating endothelial progenitor cell (EPC) counts were also documented. In both PCOS subgroups, which demonstrated hyperaggregability to ADP, responses to SNP inhibition of aggregation (the principal end-point of the study) were significantly impaired (P<0.01 for both), as were their endothelium-dependent vascular responses to salbutamol (P<0.05 for both). However, vasomotor responses to nitroglycerin and circulating EPC counts did not vary between groups. PCOS subjects also had significantly elevated ADMA, MDA and hs-CRP levels relative to normals (all P<0.05). Impairment of SNP response remained unaltered after mean 30+/-2.4 months follow-up in PCOS subjects. We conclude that in PCOS subjects, independent of obesity and associated insulin resistance, profound and reproducible impairment of platelet responsiveness to NO is an additional component of cardiovascular homeostatic disturbance.

How does blood glucose control with metformin influence intensive insulin protocols? Evidence for involvement of oxidative stress and inflammatory cytokines

INTRODUCTION

Recent investigations have revealed that control of hyperglycaemia with insulin improves outcomes. The cornerstone of hyperglycaemia in critically ill patients is insulin resistance and it remains refractory to intensive insulin protocols. We designed this study to evaluate the efficacy and safety of a new intensive insulin therapy (IIT) protocol combined with metformin.

METHODS

Twenty-one patients with systemic inflammatory response syndrome and a blood glucose level of >120 mg/dl admitted to an intensive care unit (ICU) were randomised to receive either intravenous infusion of IIT alone (n=11) or combined with metformin (IIT+MET; n=10) to maintain a blood glucose level (BGL) of 80-120 mg/dl. Blood samples were obtained at baseline and at 48 hours, 96 hours and 7 days after initiation of the study. Samples were analysed for interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-alpha) and nitric oxide (NO) as inflammatory mediators; plasminogen activation inhibitor-1 (PAI-1) as a coagulation mediator; and thiobarbituric reactive substances (TBARS), total antioxidant power (TAP) and total thiol molecules (TTM) as oxidative stress parameters.

RESULTS

The addition of metformin to the IIT protocol decreased insulin requirement and concentration of insulin and C-peptide. With both treatments at most time points, the mean plasma levels of IL-6, TNF-alpha, NO, PAI-1 and TBARS were found to be significantly lower compared with baseline. Antioxidant activity was increased in both arms with increasing TAP and TTM (P<0.05). There was no significant difference between the two groups regarding reported beneficial effects on these parameters. Therapeutic Intervention Scoring System-28 (TISS-28) score, an index of nursing workload and number of therapeutic interventions, decreased in the IIT+MET group (P<0.01). We did not observe any occurrence of hyperlactataemia or acidosis in the IIT+MET group.

CONCLUSION

Metformin plus insulin appears to lower the incidence of insulin resistance, lower insulin requirement while maintaining blood glucose level control, and consequently lower the incidence of adverse effects related to high-dose insulin therapy, particularly hypoglycaemia, and also declined nursing workload. Both treatment protocols showed improvements in inflammatory cytokine levels. Further studies with larger sample sizes are warranted to determine the undiscovered facts of insulin-sensitising agents in critically ill patients.