Insulin resistance and glucose-induced thermogenesis in critical illness

Impact of the triglyceride-glucose index on 28-day mortality in non-diabetic critically Ill patients with sepsis: a retrospective cohort analysis

INTRODUCTION

Sepsis is a life-threatening condition that poses a globally high mortality rate. Identifying risk factors is crucial. Insulin resistance and the TYG index, associated with metabolic disorders, may play a role. This study explores their correlation with mortality in non-diabetic septic patients.

METHODS

This retrospective cohort study used data from the MIMIC-IV (version 2.1) database, which includes over 50,000 ICU admissions from 2008 to 2019 at Beth Israel Deaconess Medical Center in Boston. We included adult patients with sepsis who were admitted to the intensive care unit in the study. The primary outcome was to evaluate the ability of TYG to predict death at 28-day of hospital admission in patients with sepsis.

RESULTS

The study included 2213 patients with sepsis, among whom 549 (24.8%) died within 28 days of hospital admission. We observed a non-linear association between TYG and the risk of mortality. Compared to the reference group (lower TYG subgroup), the 28-day mortality increased in the higher TYG subgroup, with a fully adjusted hazard ratio of 2.68 (95% CI: 2.14 to 3.36). The area under the curve (AUC) for TYG was 67.7%, higher than for triglycerides alone (AUC = 64.1%), blood glucose (AUC = 62.4%), and GCS (AUC = 63.6%), and comparable to SOFA (AUC = 69.3%). The final subgroup analysis showed no significant interaction between TYG and each subgroup except for the COPD subgroup (interaction P-values: 0.076-0.548).

CONCLUSION

In our study, TYG can be used as an independent predictor for all-cause mortality due to sepsis within 28 days of hospitalization.

The triglyceride-glucose index: a novel predictor of stroke and all-cause mortality in liver transplantation recipients

BACKGROUND

The triglyceride-glucose (TyG) index, identified as a reliable indicator of insulin resistance (IR), was reported to be associated with stroke recurrence and morbidity in the general population and critically ill patients. However, the relationship in liver transplantation (LT) recipients remains unknown. This study aimed to investigate the correlation between the TyG index and post-LT stroke along with all-cause mortality and further assess the influence of IR on the LT recipients' prognosis.

METHODS

The retrospective cohort study enrolled 959 patients who underwent LT at a university-based medical centre between January 2015 and January 2021. The participants were divided into three groups according to their TyG index tertiles. The primary outcome was post-LT stroke. Multivariate logistic regression, COX proportional hazards regression, and restricted cubic spline RCS were used to examine the association between the TyG index and outcomes in LT recipients.

RESULTS

With a median TyG index of 8.23 (7.78-8.72), 780 (87.18% males) patients were eventually included. The incidence of post-LT stroke was 5.38%, and the in-hospital, 1-year, and 3-year mortality rates were 5.54%, 13.21%, and 15.77%, respectively. Multivariate regression analysis showed an independent association between the TyG index and an increased risk of post-LT stroke [adjusted odds ratio (aOR), 3.398 (95% confidence interval [CI]: 1.371-8.426) P = 0. 008], in-hospital mortality [adjusted hazard ratio (aHR), 2.326 (95% CI: 1.089-4.931) P = 0.025], 1-year mortality [aHR, 1.668 (95% CI: 1.024-2.717) P = 0.039], and 3-year mortality [aHR, 1.837 (95% CI: 1.445-2.950) P = 0.012]. Additional RCS analysis also suggested a linear increase in the risk of postoperative stroke with elevated TyG index (P for nonlinearity = 0.480).

CONCLUSIONS

The TyG index may be a valuable and reliable indicator for assessing stroke risk and all-cause mortality in patients undergoing LT, suggesting its potential relevance in improving risk stratification during the peri-LT period.

Triglyceride-glucose index linked to all-cause mortality in critically ill patients: a cohort of 3026 patients

BACKGROUND

Triglyceride-glucose (TyG) index as a reliable surrogate of insulin resistance (IR) has been shown to be related to adverse clinical outcomes in patients with acute coronary syndrome, heart failure, ischemic stroke and so on. However, the relationship between TyG index and all-cause mortality in intensive care unit (ICU) patients remains unknown. The purpose of this study was to investigate the correlation between TyG index and all-cause mortality to evaluate the impact of IR on the prognosis of this population.

METHODS

This was a retrospective observational study that included 3026 patients who had an initial triglyceride and glucose data on the first day of ICU admission, and all data were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. These patients were grouped into quartiles (Q1-Q4) according to TyG index. The Kaplan-Meier analysis was used to compare all-cause mortality among the above four groups. Cox proportional hazards analyses were performed to examine the association between TyG index and all-cause mortality.

RESULTS

During 10.46 years of follow-up, 1148 (37.9%) patients died, of which 350 (11.6%) occurred during the hospital stay and 258 (8.5%) occurred during the ICU stay. Kaplan-Meier analysis showed that the risk of all-cause mortality was significantly higher in patients with higher TyG index (log-rank P = 0.021). Multivariable Cox proportional hazards analyses showed that the TyG index was an independent risk predictor of ICU death (HR: 1.72, 95% CI 1.18-2.52, P = 0.005) and hospital death (HR: 2.19, 95% CI 1.59-3.03, P < 0.001), and each 1-unit increased in the TyG index, a 1.19-fold increase in the risk of death during the hospital stay.

CONCLUSIONS

TyG index is strongly related to the all-cause mortality increasing in critically ill patients. This finding indicates that the TyG index might be useful in identifying people at high risk of ICU death and hospital death.

Metabolic Support of the Patient on Continuous Renal Replacement Therapy

Continuous renal replacement therapy (CRRT) is the modality of choice in critically ill patients with hemodynamic instability requiring renal replacement therapy. The goal of this review is to discuss an overview of CRRT types, components, and important considerations for nutrition support provision. Evidence basis for guidelines and our recommendations are reviewed. Nutrition support-related implications include the possibility of calorie gain with citrate-based anticoagulation, calorie loss with glucose-free replacement fluids and dialysate, and significant amino acid losses in effluent. We challenge nutrition support clinicians to develop a keen understanding of the specific CRRT modalities that are employed in their intensive care units and to be able to determine how the CRRT prescription may impact a patient's nutrition support prescription.

Energy, Protein, Carbohydrate, and Lipid Intakes and Their Effects on Morbidity and Mortality in Critically Ill Adult Patients: A Systematic Review

The guidelines for nutritional support in critically ill adult patients differ in various aspects. The optimal amount of energy and nutritional substrates supplied is important for reducing morbidity and mortality, but unfortunately this is not well known, because the topic is complex and every patient is individual. The aim of this review was to gather recent pertinent information concerning the nutritional support of critically ill patients in the intensive care unit (ICU) with respect to the energy, protein, carbohydrate, and lipid intakes and the effect of their specific utilization on morbidity and mortality. Enteral nutrition (EN) is generally recommended over parenteral nutrition (PN) and is beneficial when administered within 24-48 h after ICU admission. In contrast, early PN does not provide substantial advantages in terms of morbidity and mortality, and the time when it is safe and beneficial remains unclear. The most advantageous recommendation seems to be administration of a hypocaloric (<20 kcal · kg^-1 · d^-1), high-protein diet (amino acids at doses of ≥2 g · kg^-1 · d^-1), at least during the first week of critical illness. Another important factor for reducing morbidity is the maintenance of blood glucose concentrations at 120-150 mg/dL, which is accomplished with the use of insulin and lower doses of glucose of 1-2 g · kg^-1 · d^-1, because this prevents the risk of hypoglycemia and is associated with a better prognosis according to recent studies. A fat emulsion is used as a source of required calories because of insulin resistance in the majority of patients. In addition, lipid oxidation in these patients is ∼25% higher than in healthy subjects.

Post-burn hepatic insulin resistance is associated with endoplasmic reticulum (ER) stress

Insulin resistance with its associated hyperglycemias represents one significant contributor to mortality in burned patients. A variety of cellular stress-signaling pathways are activated as a consequence of burn. A key player in the cellular stress response is the endoplasmic reticulum (ER). Here, we investigated a possible role for ER-stress pathways in the progression of insulin function dysregulation postburn. Rats received a 60% total body surface area thermal injury, and a laparotomy was performed at 24, 72, and 192 h postburn. Liver was harvested before and 1 min after insulin injection (1 IU/kg) into the portal vein, and expression patterns of various proteins known to be involved in insulin and ER-stress signaling were determined by Western blotting. mRNA expression of glucose-6-phosphatase and glucokinase were determined by reverse-transcriptase-polymerase chain reaction and fasting serum glucose and insulin levels by standard enzymatic and enzyme-linked immunosorbent assay techniques, respectively. Insulin resistance indicated by increased glucose and insulin levels occurred starting 24 h postburn. Burn injury resulted in activation of ER stress pathways, reflected by significantly increased accumulation of phospho-PKR-like ER-kinase and phosphorylated inositol requiring enzyme 1, leading to an elevation of phospho-c-Jun N-terminal kinase and serine phosphorylation of insulin receptor substrate (IRS) 1 postburn. Insulin administration caused a significant increase in tyrosine phosphorylation of IRS-1, leading to activation of the phosphatidylinositol 3 kinase/Akt pathway in normal liver. Postburn tyrosine phosphorylation of IRS-1 was significantly impaired, associated with an inactivation of signaling molecules acting downstream of IRS-1, leading to significantly elevated transcription of glucose-6-phosphatase and significantly decreased mRNA expression of glucokinase. Activation of ER-stress signaling cascades may explain metabolic abnormalities involving insulin action after burn.

What, how, and how much should patients with burns be fed?

The hypermetabolic response to severe burn injury is characterized by hyperdynamic circulation and profound metabolic, physiologic, catabolic, and immune system derangements. Failure to satisfy overwhelming energy and protein requirements after, and during, severe burn injury results in multiorgan dysfunction, increased susceptibility to infection, and death. Attenuation of the hypermetabolic response by various pharmacologic modalities is emerging as an essential component of the management of patients with severe burn injury. This review focuses on the more recent advances in therapeutic strategies to attenuate the hypermetabolic response and its postburn-associated insulin resistance.

Abnormal insulin sensitivity persists up to three years in pediatric patients post-burn

CONTEXT

The acute hypermetabolic response post-burn is associated with insulin resistance and hyperglycemia, significantly contributing to adverse outcome of these patients.

OBJECTIVE

The aim of the study was to examine the persistence of abnormalities of various clinical parameters commonly utilized to assess the degree of insulin resistance in severely burned children for up to 3 yr after the burn injury.

DESIGN, SETTING AND PATIENTS

A total of 194 severely burned pediatric patients, admitted to our institute between 2002 and 2007, were enrolled in this prospective study and compared to a cohort of 95 nonburned, noninjured children.

MAIN OUTCOME MEASURES

Urinary cortisol, epinephrine, and norepinephrine, serum cytokines, and resting energy requirements were determined at admission and 1, 2, 6, 9, 12, 18, 24, and 36 months post-burn. A 75-g oral glucose tolerance test was performed at similar time points; serum glucose, insulin, and C-peptide were measured; and insulin sensitivity indices, such as ISI Matsuda, homeostasis model assessment, quantitative insulin sensitivity check index, and ISI Cederholm, were calculated. Statistical analysis was performed by ANOVA with Bonferroni correction with significance accepted at P < 0.05.

RESULTS

Urinary cortisol and catecholamines, serum IL-7, IL-10, IL-12, macrophage inflammatory protein-1b, monocyte chemoattractant protein-1, and resting energy requirements were significantly increased for up to 36 months post-burn (P < 0.05). Glucose values were significantly augmented for 6 months post-burn (P < 0.05), associated with significant increases in serum C-peptide and insulin that remained significantly increased for 36 months compared to nonburned children (P < 0.05). Insulin sensitivity indices, ISI Matsuda, ISI quantitative insulin sensitivity check index, and homeostasis model assessment were abnormal throughout the whole study period, indicating peripheral and whole body insulin resistance. The insulinogenic index displayed physiological values, indicating normal pancreatic beta-cell function.

CONCLUSIONS

A severe burn is associated with stress-induced insulin resistance that persists not only during the acute phase but also for up to 3 yr post-burn.

The hepatic response to thermal injury: is the liver important for postburn outcomes?

Thermal injury produces a profound hypermetabolic and hypercatabolic stress response characterized by increased endogenous glucose production via gluconeogenesis and glycogenolysis, lipolysis, and proteolysis. The liver is the central body organ involved in these metabolic responses. It is suggested that the liver, with its metabolic, inflammatory, immune, and acute phase functions, plays a pivotal role in patient survival and recovery by modulating multiple pathways following thermal injury. Studies have evaluated the role and function of the liver during the postburn response and showed that liver integrity and function are essential for survival, and that hepatic acute phase proteins are strong predictors for postburn survival. This review discusses these studies and delineates the pivotal role of the liver in patients following severe thermal injury.

Insulin resistance postburn: underlying mechanisms and current therapeutic strategies

The profound hypermetabolic response to burn injury is associated with insulin resistance and hyperglycemia, significantly contributing to the incidence of morbidity and mortality in this patient population. These responses are present in all trauma, surgical, or critically ill patients, but the severity, length, and magnitude is unique for burn patients. Although advances in therapeutic strategies to attenuate the postburn hypermetabolic response have significantly improved the clinical outcome of these patients during the past years, therapeutic approaches to overcome stress-induced hyperglycemia have remained challenging. Intensive insulin therapy has been shown to significantly reduce morbidity and mortality in critically ill patients. High incidence of hypoglycemic events and difficult blood glucose titrations have led to investigation of alternative strategies, including the use of metformin, a biguanide, or fenofibrate, a peroxisome proliferator-activated receptor (PPAR)-gamma agonist. Nevertheless, weaknesses and potential side affects of these drugs reinforces the need for better understanding of the molecular mechanisms underlying insulin resistance postburn that may lead to novel therapeutic strategies further improving the prognosis of these patients. This review aims to discuss the mechanisms underlying insulin resistance induced hyperglycemia postburn and outlines current therapeutic strategies that are being used to modulate hyperglycemia after thermal trauma.

Severity of insulin resistance in critically ill medical patients

Critical illness is characterized by a hypermetabolic state associated with increased mortality, which is partly ascribed to the occurrence of hyperglycemia caused by enhanced endogenous glucose production and insulin resistance (IR). Insulin resistance is well described in patients after surgery and trauma. However, it is less clearly quantified in critically ill medical patients. In this clinical cohort study, IR (M value) was quantified in 40 critically ill medical patients and 25 matched, healthy controls by isoglycemic hyperinsulinemic clamps after an overnight fast on the day after admission to a medical intensive care unit. Energy and substrate metabolism were measured by using indirect calorimetry in the patients before and during the clamp. The severity of illness was assessed by the acute physiology and chronic health evaluation (APACHE) III score. M values of critically ill medical patients were significantly lower compared with healthy controls (2.29 +/- 1.0 and 7.6 +/- 2.9 mg/kg per minute, respectively; P < .001) and were closely related to APACHE III scores (r = -0.43, P < .01), body mass index (r = -0.41, P < .01), and resting energy expenditure (r = 0.40, P < .05). The M value was not associated with age, basal glucose concentrations, and respiratory quotient, and it did not differ among patients with various admission diagnoses. In conclusion, insulin sensitivity was found to be reduced by 70% in critically ill medical patients. The severity of IR was associated with the severity of illness, body mass index, and resting energy expenditure, but not with substrate oxidation rates. In addition, the severity of IR did not vary among patients with different admission diagnoses.

Metabolic and Hemodynamic Effects of High-Dose Insulin Treatment in Aortic Valve and Coronary Surgery

BACKGROUND

Glucose and insulin have been used as an adjuvant therapy in cardiac surgery because of their potentially beneficial effects on myocardial metabolism and contractile function. This study evaluated the effects of high-dose insulin on systemic metabolism and hemodynamics after combined heart surgery.

METHODS

Forty elective patients scheduled for combined aortic valve replacement and coronary artery bypass surgery were randomly assigned to receive either high-dose insulin treatment (short-acting insulin 1 IU.kg(-1).h(-1) with 30% glucose 1.5 mL.kg(-1).h(-1) administered separately) or control treatment (saline). The blood glucose levels were maintained within a targeted range by adjusting the rate of glucose infusion in the treatment group and by short-acting insulin bolus doses in the control group.

RESULTS

The lactate clearance was faster (p = 0.046), and the lactate levels (p = 0.016), blood glucose levels (p < 0.001), and free fatty acid levels (p < 0.001) were lower in the insulin group postoperatively. Besides, there was lesser need for dobutamine support (p = 0.013) and a trend toward better cardiac indices. Insulin treatment increased the respiratory quotient (p < 0.001), but there were no differences between the groups with regard to systemic oxygen consumption or energy expenditure measured by indirect calorimetry. The average glucose uptake in the insulin group was 7.1 g/kg in 24 hours (28 kcal.kg(-1).day(-1)).

CONCLUSIONS

The high-dose insulin treatment was associated with lower blood glucose levels, better preserved myocardial contractile function, and less need for inotropic support, and hence led to lower lactate levels postoperatively. The protocol is safe, but requires strict control of blood glucose level.