Effect of modified glucose-insulin-potassium on free fatty acids, matrix metalloproteinase, and myoglobin in ST-elevation myocardial infarction

Stress-Induced Hyperglycaemia in Non-Diabetic Patients with Acute Coronary Syndrome: From Molecular Mechanisms to New Therapeutic Perspectives

Stress-induced hyperglycaemia (SIH) at hospital admission for acute coronary syndrome is associated with poor outcome, especially in patients without known diabetes. Nevertheless, insulin treatment in these subjects was not correlated with the reduction of mortality. This is likely due to the fact that SIH in the context of an acute coronary syndrome, compared to that in known diabetes, represents an epiphenomenon of other pathological conditions, such as adrenergic and renin-angiotensin system over-activity, hyperglucagonaemia, increase of circulating free fatty acids and pancreatic beta-cell dysfunction, which are not completely reversed by insulin therapy and so worsen the prognosis. Thus, SIH may be considered not only as a biomarker of organ damage, but also as an indicator of a more complex therapeutic strategy in these subjects. The aim of this review is to analyse the molecular mechanisms by which SIH may favour a worse prognosis in non-diabetic patients with acute coronary syndrome and identify new therapeutic strategies, in addition to insulin therapy, for a more appropriate treatment and improved outcomes.

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

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

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.

Intensive management of hyperglycaemia in acute coronary syndromes. Study design and rationale of the BIOMArCS 2 glucose trial

BACKGROUND

Elevated admission plasma glucose is associated with increased mortality in patients who are admitted with an acute coronary syndrome. This may be mediated by increased inflammation, apoptosis and coagulation, and by a disturbed endothelial function that can be found in hyperglycaemic patients. Insulin has several characteristics that may potentially counteract these mechanisms.

METHODS

The BIOMArCS programme is a multi-centre initiative and currently consists of three different studies. The effects of acute coronary syndrome on acute biomarkers washout are studied in the BIOMArCS pilot and the value of biomarkers in predicting upcoming acute coronary syndrome events is studied in BIOMArCS 1. The third study (BIOMArCS 2 glucose), which will be presented here, investigates the effectiveness and safety of intensive glucose level control compared with conventional glucose management in patients with acute coronary syndrome and an admission plasma glucose of 7.8-16 mmol/l. In BIOMArCS 2 glucose, a total of 300 patients without insulin-treated diabetes mellitus will be randomized in a 1:1 ratio to either intensive or conventional glucose management on top of standard medical care. The primary endpoint is infarct size as expressed by the cardiac troponin T level 72 h after admission. To study the metabolic effects of insulin administration, we will investigate biomarker washout patterns of various metabolic mechanisms up to 7 days after admission. These markers will address inflammation, oxidative stress, hypercoagulability, endothelial activation and vasodilatation.

IMPLICATIONS

Current acute coronary syndrome guidelines lack a clear strategy for hyperglycaemia treatment. This study will extend our knowledge on this matter as it may clarify mechanisms and generate hypotheses of if and how myocardial infarct size may be limited by glucose management at admission.

Brain insulin controls adipose tissue lipolysis and lipogenesis

White adipose tissue (WAT) dysfunction plays a key role in the pathogenesis of type 2 diabetes (DM2). Unrestrained WAT lipolysis results in increased fatty acid release, leading to insulin resistance and lipotoxicity, while impaired de novo lipogenesis in WAT decreases the synthesis of insulin-sensitizing fatty acid species like palmitoleate. Here, we show that insulin infused into the mediobasal hypothalamus (MBH) of Sprague-Dawley rats increases WAT lipogenic protein expression, inactivates hormone-sensitive lipase (Hsl), and suppresses lipolysis. Conversely, mice that lack the neuronal insulin receptor exhibit unrestrained lipolysis and decreased de novo lipogenesis in WAT. Thus, brain and, in particular, hypothalamic insulin action play a pivotal role in WAT functionality.

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.

Insulin—Blood Cardioplegia Decreases Matrix Metalloproteinase Activity in Ischaemia-reperfusion Injury during Coronary Artery Bypass Surgery

Reperfusion of myocardium during coronary bypass activates matrix metalloproteinases (MMPs) with changes occurring in the levels of tissue inhibitors of metalloproteinases (TIMPs) in the myocardium. This study investigated the effects of insulin-blood cardioplegia on MMP activity and TIMP levels during reperfusion. Non-diabetic patients undergoing coronary artery bypass graft with cardiopulmonary bypass were randomized into a control group ( n = 12) or an insulin group ( n = 12). Blood cardioplegia was used for both groups; insulin and glucose were added to the insulin group. Blood samples were obtained from the coronary sinus just before aortic cross clamping and after 1 and 30 min of reperfusion. Plasma proenzyme MMPs (proMMP-2 and −9) and TIMPs (TIMP-1 and TIMP-2) levels were measured. There were no differences between groups for MMP-2 and TIMP-2 levels. However, insulin diminished proMMP-9 activation, although some still occurred. TIMP-1 consumption lessened during reperfusion which, we conclude, was as a result of the diminished MMP activation. This is the first open heart surgery study in which diminished MMP activation was achieved via a metabolic change.

Use of insulin to improve glycemic control in diabetes mellitus

BACKGROUND

The restoration of normoglycemia ensures the control of diabetic symptoms and reduction in microangiopathic complications in type 1 and type 2 diabetes. However, there is no conclusive evidence that intensive glycemic control alone will prevent macrovascular disease, the commonest cause of morbidity and mortality in type 2 diabetes. As atherosclerosis is an inflammatory condition, it is relevant that the two common insulin resistant states of obesity and type 2 diabetes have significant inflammatory processes, which promote atherosclerosis. It is also relevant that glucose has been shown to have profound effects on the endothelial cell, the leukocyte and the platelet. These effects include the induction of acute oxidative and inflammatory stress and a prothrombotic and pro-apoptotic effect following glucose intake. In contrast insulin has been shown to exert several biological effects at physiologically relevant concentrations, in relation to the endothelial cell, the platelet and leucocyte function, which may be cardioprotective and potentially anti-atherosclerotic.

CONCLUSION

These findings are of great interest as it is possible that the prevention of macrovascular complications in type 2 diabetes may require the use of those glucose lowering drugs which have additional anti-inflammatory effects in addition to the control of comorbid conditions (hypertension and dyslipidemia) associated with this disease. Results of future clinical trials are awaited to confirm the benefits of this approach in the primary and secondary prevention of macrovascular complications in type 2 diabetes.