Insulin: an endogenous cardioprotector

Intensive Insulin Therapy in High-Risk Cardiac Surgery Patients: Evidence from the Leuven Randomized Study

Mortality and morbidity of critically ill diabetic as well as nondiabetic patients are improved when blood glucose levels are tightly controlled to normoglycemia with intensive insulin therapy during their stay in the intensive care unit (ICU). This has been demonstrated in large prospective, randomized, controlled clinical studies for adult patients admitted to surgical and medical ICUs. Particularly for cardiac surgery patients, the hospital survival benefit with insulin therapy is most pronounced and maintained up to 4 years after hospital discharge, without inducing a substantial burden for the patients, their relatives, or society. Mechanistic studies exploring the molecular pathways involved suggest that intensive insulin therapy exerts its beneficial effects mainly through the maintenance of normal blood glucose levels.

Diabetes of injury: novel insights

Critically ill patients usually develop hyperglycemia, a condition referred to as "diabetes of injury." More and more evidence argues against the concept that this is an adaptive beneficial response. Indeed, the development of hyperglycemia seems to be detrimental for the outcome of critically ill patients, because maintenance of normoglycemia with intensive insulin therapy prevents morbidity and reduces mortality of critically ill patients to a large extent. The mechanisms underlying these clinical benefits are being studied further.

Glucose-insulin-potassium therapy in the era of coronary revascularization

Glucose-insulin-potassium (GIK) utilization in the treatment of acute myocardial infarction (AMI) has been studied since the early 1960s with varying results. It is well established that ischemic myocardial cells convert from aerobic metabolism of glucose to toxic anaerobic free fatty acid (FFA) metabolism for the production of energy. It has been hypothesized that administration of GIK during coronary revascularization would decrease the degree of myocardial damage. Earlier clinical trials, before the revascularization era, demonstrated a potential role for GIK therapy to reduce the mortality and morbidity associated with AMI. In recent years, GIK therapy has been incorporated into current revascularization methods without clear evidence as to its efficacy. Based on the most current studies, it has been determined that GIK therapy is not beneficial in patients with AMI, regardless of revascularization status, and therefore should not be used.

A randomized trial of adding insulin glargine vs. avoidance of insulin in people with Type 2 diabetes on either no oral glucose-lowering agents or submaximal doses of metformin and/or sulphonylureas. The Canadian INSIGHT (Implementing New Strategies with Insulin Glargine for Hyperglycaemia Treatment) Study

AIMS

Insulin is generally withheld until people with Type 2 diabetes are unresponsive to other therapies. However, its potential advantages suggest that it could be added earlier to achieve glycaemic goals; this possibility was tested in a clinical trial.

METHODS

Consenting adults aged 18-80 years with Type 2 diabetes for at least 6 months, HbA1c of 7.5-11%, and on 0, 1 or 2 oral agents, were randomized to one of two therapeutic approaches for 24 weeks: evening insulin glargine plus self-titration by 1 unit/day if the fasting plasma glucose (FPG) was > 5.5 mmol/l; or conventional therapy with physician adjustment of oral glucose-lowering agents if capillary FPG levels were > 5.5 mmol/l. The primary outcome was the first achievement of two consecutive HbA1c levels <or= 6.5%.

RESULTS

Two hundred and six participants were allocated to glargine and 199 to oral agents. Compared with control subjects, participants receiving glargine: (i) were 1.68 times more likely to achieve two consecutive HbA1c levels <or= 6.5% (95% CI 1.00-2.83; P = 0.049); (ii) reduced their HbA1c by 1.55 vs. 1.25% (P = 0.005), achieving adjusted means of 7.0 vs. 7.2% (P = 0.0007); (iii) had lower FPG (P = 0.0001), non-high-density lipoprotein (HDL) cholesterol (P = 0.02) and triglycerides (P = 0.02); (iv) had greater increases in treatment satisfaction (P = 0.045); and (v) had a 1.9-kg greater increase in weight (P < 0.0001). No differences in hypoglycaemia were noted.

CONCLUSIONS

Adding insulin glargine is more likely to achieve a lower HbA(1c) level than conventional therapy with oral agents.

Is pyruvate an endogenous anti-inflammatory molecule?

Pyruvic acid is an effective scavenger of reactive oxygen species. Ethyl pyruvate has demonstrated anti-inflammatory actions and improved hyperpermeability and bacterial translocation due to endotoxemia and is of benefit in animal models of sepsis and septic shock. Ethyl pyruvate specifically inhibits tumor necrosis factor-alpha production and decreases circulating levels of high-mobility group box-1 and nuclear factor-kappaB signaling pathways by specifically targeting its p65 subunit in animals with established endotoxemia or sepsis and in macrophage cultures. Ethyl pyruvate also decreases cyclo-oxygenase-2, inducible nitric oxide synthase, and interleukin-6 mRNA expression in the liver, ileal mucosa, and colonic mucosa in animal models with hemorrhagic shock. Similar beneficial actions have been seen in endotoxemia. These and other studies suggest that ethyl pyruvate could be of significant benefit in the treatment of patients who are critically ill and have sepsis/septic shock.

Glucose-insulin and potassium infusions in septic shock

Glucose-insulin and potassium (GIK) infusions are beneficial in treating ischemic myocardial depression. Myocardial depression is also an important feature in septic shock. We describe two cases of pressor-resistant hypodynamic septic shock that responded to high-dose GIK infusions. In each case, hemodynamic profiles improved sufficiently to allow withdrawal of vasopressor agents. Further assessment of GIK in patients with hypodynamic septic shock is necessary to confirm efficacy and prognostic significance.

Survival benefits of intensive insulin therapy in critical illness: impact of maintaining normoglycemia versus glycemia-independent actions of insulin

Tight blood glucose control with insulin reduces morbidity and mortality of critically ill patients. However, the relative impact of maintaining normoglycemia and of glycemia-independent actions of insulin remains unknown. We therefore independently manipulated blood glucose and plasma insulin levels in burn-injured, parentally fed rabbits over 7 days to obtain four study groups: two normoglycemic groups with either normal or elevated insulin levels and two hyperglycemic groups with either normal or elevated insulin levels. We studied the relative impact of glycemia and glycemia-independent effects of insulin on survival; myocardial contractility in an open chest preparation; endothelial function in isolated aortic rings; and liver, kidney, and leukocyte function in a rabbit model of critical illness. Mortality was significantly lower in the two normoglycemic groups independent of insulin levels. Maintaining normoglycemia, independent of insulin levels, prevented endothelial dysfunction as well as liver and kidney injury. To increase myocardial systolic function, elevated insulin levels and prevention of hyperglycemia were required concomitantly. Leukocyte dysfunction was present in the two hyperglycemic groups, which could in part be rescued by insulin. The results suggest that the observed benefits of intensive insulin therapy required mainly maintenance of normoglycemia; whereas glycemia-independent actions of insulin exerted only minor, organ-specific impact.

Glucose metabolism and insulin therapy

Hyperglycemia is a common feature of the critically ill patient and has been associated with increased mortality. Maintaining normoglycemia with insulin therapy improves survival and reduces morbidity in surgical ICU patients, as shown by a large randomized controlled study. Prevention of glucose toxicity by strict glycemic control but also other metabolic and non-metabolic effects of insulin contribute to these clinical benefits.

The significance of glucose, insulin and potassium for immunology and oncology: a new model of immunity

Background

A recent development in critical care medicine makes it urgent that research into the effect of hormones on immunity be pursued aggressively. Studies have demonstrated a large reduction in mortality as a result of infusion with glucose, insulin and potassium. Our work in the oncology setting has led us to propose that the principal reason for such an effect is that GIK stimulates lymphocytes to proliferate and attack pathogens, sparing the patient the stress of infection. That suggestion is based on a new model of immunity that describes the effect of hormones on lymphocytes. We hypothesized that the application of glucose, insulin, thyroid and potassium would awaken inert tumor infiltrating lymphocytes to destroy the tumor.

Methods

The antitumor effect of a thyroxine, glucose, insulin, and potassium (TGIK) combination was studied in a series of controlled experiments in murine models of tumor progression to assess the biologic activity of the formulation, the effect of route of administration, the effect on tumor type, and the requirement for insulin in the TGIK formulation.

Results

Melanoma and colon tumors inoculated with TGIK were significantly reduced in size or retarded in growth compared to controls injected with saline. I.P. and I.M. injections showed that the formulation had no effect systemically at the doses administered.

Conclusion

We conclude that TGIK has anti-tumor activity when administered intratumorally, probably by stimulating lymphocytes to attack tumors. This is similar to the effect of GIK on reducing sepsis in critical care patients. We suggest that when GIK is administered exogenously, it restores immune competence to the critically ill or cancer patient and causes destruction of pathogens or tumors, while endogenous resources are devoted to repair. This implies that hormonal therapy may be useful in treating various other pathologies involving immune suppression, as well as malignancies. We also propose research that could bring resolution of the controversy over mechanism and point the way to new therapeutic strategies for numerous diseases including chronic infections and auto-immune diseases.

Glycemic and nonglycemic effects of insulin: how do they contribute to a better outcome of critical illness?

PURPOSE OF REVIEW

This review gives an overview of the clinical outcome benefits associated with intensive insulin therapy administered to critically ill patients and of the progress in the unraveling of the mechanisms underlying these positive effects.

RECENT FINDINGS

In a large, prospective, randomized, controlled study, strict blood glucose control with intensive insulin therapy strongly reduced mortality and morbidity of surgical intensive care patients. These results were recently confirmed in a more heterogeneous patient population admitted to a mixed medical-surgical intensive care unit. Most of the clinical benefits of intensive insulin therapy appear to be related to prevention of hyperglycemia, which has been demonstrated to adversely affect outcome. Part of the improvement is related to protection of the mitochondrial compartment and innate immunity from glucose toxicity. Also, direct insulin effects contribute to the improved outcome. The beneficial nonglycemic metabolic actions of insulin include a partial correction of the abnormal serum lipid profile and counteraction of the catabolic state evoked by critical illness. The prevention of excessive inflammation and myocardial protection illustrate other nonmetabolic direct anti-inflammatory and anti-apoptotic properties of insulin, although lowering of glucose levels may have played a role in these events as well.

SUMMARY

Substantial progress has been made in the understanding of the mechanisms underlying the improved survival and reduced morbidity with intensive insulin therapy in critical illness. More studies, however, are needed to further elucidate the exact pathways involved and the relative contribution of prevention of glucose toxicity and direct nonglycemic effects of insulin.

High-Dose Insulin Therapy for Calcium-Channel Blocker Overdose

OBJECTIVE:

To evaluate the evidence for using high-dose insulin therapy with supplemental dextrose and potassium in calcium-channel blocker (CCB) overdose.

DATA SOURCES:

Evidence of efficacy for high-dose insulin therapy with supplemental dextrose and potassium was sought by performing a search of MEDLINE and Toxline between 1966 and July 2004 using combinations of the terms calcium-channel blocker, overdose, poisoning, antidote, and insulin. Abstracts from the North American Congress of Clinical Toxicology for the years 1996–2003 were also reviewed.

STUDY SELECTION AND DATA EXTRACTION:

Identified articles, including animal studies, case reports, and case series, were evaluated for this review. No clinical trials were available.

DATA SYNTHESIS:

Animal models of CCB overdose demonstrate that high-dose insulin with supplemental dextrose and potassium was a more effective therapy than calcium, glucagon, or catecholamines. High-dose insulin appears to enhance cardiac carbohydrate metabolism and has direct inotropic effects. Published clinical experience is limited to 13 case reports where insulin was used after other therapies were failing; 12 of these patients survived. High-dose insulin therapy was beneficial for CCB-induced hypotension, hyperglycemia, and metabolic acidosis. Bradycardia and heart block resolved in some patients, but persisted in others.

CONCLUSIONS:

Based on animal data and limited human experience, as well as the inadequacies of available alternatives for patients with significant poisoning, high-dose insulin therapy warrants further study and judicious use in patients with life-threatening CCB poisoning.

Endocrine interventions in the ICU

Patients with critical illness, particularly those who depend on intensive care for a prolonged period of time, have a high morbidity and mortality. The acute and chronic phases of critical illness are associated with distinct endocrine alterations. Acute endocrine adaptations to the severe stress of critical illness, comprising an activated anterior pituitary function, have been selected by nature and can, as such, be considered as beneficial for surviving. These adaptations disappear or wane during the prolonged phase of critical illness. In this phase there is a reduced pulsatile secretion of different anterior pituitary hormones and the so-called "wasting syndrome" occurs. This prolonged endocrine/metabolic stress response is quite different from the acute response and may, to some extent, no longer be adaptive. Intervention within the endocrine system, however, remains highly controversial, as it is difficult to differentiate between beneficial adaptations and harmful abnormalities and to outline strategies for therapy. Insulin infusion titrated to maintain normoglycemia may be a notable exception, as this intervention has been proven to increase survival and reduce morbidity of surgical intensive care patients. Treatment of "relative adrenal failure" with hydrocortisone also appears to improve the outcome of patients with septic shock, but diagnostic and dosing issues still remain unresolved. Although extensive research has shown that infusion of hypothalamic-releasing peptides is able to restore physiological hormonal patterns within the somatotropic, thyrotropic, and gonadal axes and, thereby, to generate a controlled anabolic response, further research is needed to investigate whether such interventions actually improve the outcome of critical illness.

Insulin therapy in people who have dysglycemia and type 2 diabetes mellitus: can it offer both cardiovascular protection and beta-cell preservation?

Mounting evidence suggests that insulin therapy may reduce risk for CV events while preserving beta-cell function, and several continuing long-term CV trials are testing these hypotheses explicitly.

Emergency care in pediatric septic shock

Septic shock causes more deaths in children than cancer. However, studies have shown that mortality can be significantly reduced by adhering to the American College of Critical Care Medicine/Pediatric Advanced Life Support guidelines. This article reviews the definitions, pathophysiology, and emergency management of children with septic shock, including the controversial role of steroids.

Association of timing, duration, and intensity of hyperglycemia with intensive care unit mortality in critically ill children

OBJECTIVE

To study the association of timing, duration, and intensity of hyperglycemia with pediatric intensive care unit (PICU) mortality in critically ill children.

DESIGN

Retrospective cohort study.

SETTING

PICU of a university-affiliated, tertiary care, children's hospital.

PATIENTS

A total of 152 critically ill children receiving vasoactive infusions or mechanical ventilation.

INTERVENTIONS

None.

METHODS

With institutional review board approval, we reviewed a cohort of 179 consecutive children, 1 mo to 21 yrs of age, treated with mechanical ventilation or vasoactive infusions. We excluded 18 with <3 microg.kg(-1).min(-1) dopamine only, diabetes, or solid organ transplant and nine who died within 24 hrs of PICU admission. Peak blood glucose (BG) and time to peak BG during PICU admission, duration of hyperglycemia (percentage of PICU days with any BG of >126 mg/dL), and intensity of hyperglycemia (median BG during first 48 PICU hours) were analyzed for association with PICU mortality using chi-square, Student's t-test, and logistic regression.

MEASUREMENTS AND MAIN RESULTS

Peak BG of >126 mg/dL occurred in 86% of patients. Compared with survivors, nonsurvivors had higher peak BG (311 +/- 115 vs. 205 +/- 80 mg/dL, p <.001). Median time to peak BG was similar in nonsurvivors (23.5 hrs; interquartile ratio, 5-236 hrs) and survivors (19 hrs; interquartile ratio, 6-113 hrs). Duration of hyperglycemia was longer in nonsurvivors (71% +/- 14% of PICU days) vs. survivors (37% +/- 5% of PICU days, p <.001). Nonsurvivors had more intense hyperglycemia during the first 48 hrs in the PICU (126 +/- 38 mg/dL) vs. survivors (116 +/- 34 mg/dL, p <.05). Univariate logistic regression analysis showed that peak BG and the duration and intensity of hyperglycemia were each associated with PICU mortality (p <.05). Multivariate modeling controlling for age and Pediatric Risk of Mortality scores showed independent association of peak BG and duration of hyperglycemia with PICU mortality (p <.05).

CONCLUSIONS

Hyperglycemia is common in critically ill children. Peak BG and duration of hyperglycemia are independently associated with mortality in our PICU. A prospective, randomized trial of strict glycemic control in this subset of critically ill children who are at high risk of mortality is both warranted and feasible.