Energy metabolism in sepsis and injury

Computational modeling of targeted temperature management in post-cardiac arrest patients

Our core body temperature is held around [Formula: see text]C by an effective internal thermoregulatory system. However, various clinical scenarios have a more favorable outcome under external temperature regulation. Therapeutic hypothermia, for example, was found beneficial for the outcome of resuscitated cardiac arrest patients due to its protection against cerebral ischemia. Nonetheless, practice shows that outcomes of targeted temperature management vary considerably in dependence on individual tissue damage levels and differences in therapeutic strategies and protocols. Here, we address these differences in detail by means of computational modeling. We develop a multi-segment and multi-node thermoregulatory model that takes into account details related to specific post-cardiac arrest-related conditions, such as thermal imbalances due to sedation and anesthesia, increased metabolic rates induced by inflammatory processes, and various external cooling techniques. In our simulations, we track the evolution of the body temperature in patients subjected to post-resuscitation care, with particular emphasis on temperature regulation via an esophageal heat transfer device, on the examination of the alternative gastric cooling with ice slurry, and on how anesthesia and the level of inflammatory response influence thermal behavior. Our research provides a better understanding of the heat transfer processes and therapies used in post-cardiac arrest patients.

The Regulatory Roles of PPARs in Skeletal Muscle Fuel Metabolism and Inflammation: Impact of PPAR Agonism on Muscle in Chronic Disease, Contraction and Sepsis

The peroxisome proliferator-activated receptor (PPAR) family of transcription factors has been demonstrated to play critical roles in regulating fuel selection, energy expenditure and inflammation in skeletal muscle and other tissues. Activation of PPARs, through endogenous fatty acids and fatty acid metabolites or synthetic compounds, has been demonstrated to have lipid-lowering and anti-diabetic actions. This review will aim to provide a comprehensive overview of the functions of PPARs in energy homeostasis, with a focus on the impacts of PPAR agonism on muscle metabolism and function. The dysregulation of energy homeostasis in skeletal muscle is a frequent underlying characteristic of inflammation-related conditions such as sepsis. However, the potential benefits of PPAR agonism on skeletal muscle protein and fuel metabolism under these conditions remains under-investigated and is an area of research opportunity. Thus, the effects of PPARγ agonism on muscle inflammation and protein and carbohydrate metabolism will be highlighted, particularly with its potential relevance in sepsis-related metabolic dysfunction. The impact of PPARδ agonism on muscle mitochondrial function, substrate metabolism and contractile function will also be described.

2-Hydroxyglutarate Metabolism Is Altered in an in vivo Model of LPS Induced Endotoxemia

The metabolic response to endotoxemia closely mimics those seen in sepsis. Here, we show that the urinary excretion of the metabolite 2-hydroxyglutarate (2HG) is dramatically suppressed following lipopolysaccharide (LPS) administration in vivo, and in human septic patients. We further show that enhanced activation of the enzymes responsible for 2-HG degradation, D- and L-2-HGDH, underlie this effect. To determine the role of supplementation with 2HG, we carried out co-administration of LPS and 2HG. This co-administration in mice modulates a number of aspects of physiological responses to LPS, and in particular, protects against LPS-induced hypothermia. Our results identify a novel role for 2HG in endotoxemia pathophysiology, and suggest that this metabolite may be a critical diagnostic and therapeutic target for sepsis.

Variability of mitochondrial respiration in relation to sepsis-induced multiple organ dysfunction

Ample experimental evidence suggests that sepsis could interfere with any mitochondrial function; however, the true role of mitochondrial dysfunction in the pathogenesis of sepsis-induced multiple organ dysfunction is still a matter of controversy. This review is primarily focused on mitochondrial oxygen consumption in various animal models of sepsis in relation to human disease and potential sources of variability in experimental results documenting decrease, increase or no change in mitochondrial respiration in various organs and species. To date, at least three possible explanations of sepsis-associated dysfunction of the mitochondrial respiratory system and consequently impaired energy production have been suggested: 1. Mitochondrial dysfunction is secondary to tissue hypoxia. 2. Mitochondria are challenged by various toxins or mediators of inflammation that impair oxygen utilization (cytopathic hypoxia). 3. Compromised mitochondrial respiration could be an active measure of survival strategy resembling stunning or hibernation. To reveal the true role of mitochondria in sepsis, sources of variability of experimental results based on animal species, models of sepsis, organs studied, or analytical approaches should be identified and minimized by the use of appropriate experimental models resembling human sepsis, wider use of larger animal species in preclinical studies, more detailed mapping of interspecies differences and organ-specific features of oxygen utilization in addition to use of complex and standardized protocols evaluating mitochondrial respiration.

Real-time Temperature Measurements of HMEC-1 Cells during Inflammation Production and Repair detected by Wireless Thermometry

Cell inflammation process is reflected through real-time in situ cellular temperature changes.

METHODS

A wireless thermometry system for in situ cellular temperature measurements was used in an incubator to detect the HMEC-1 cellular temperature under lipopolysaccharide inflammation production and norepinephrine for inflammation repair. Combining the changes in cell viability, inflammatory factor levels and ATP content caused by different lipopolysaccharide or norepinephrine doses, an obvious inflammatory response and repair effect was obtained. Temperature variations were correlated with ATP content.

RESULTS

An obvious inflammatory response with a lipopolysaccharide concentration of 0.1 mg/L and an optimal repair effect with 1 μM norepinephrine were obtained. The relationship between temperature changes and ATP content were quite different during the production of inflammation in HMEC-1 cells, having an approximately linear relationship, while under conditions of inflammation repair in HMEC-1 cells, there was an obvious nonlinear relationship.

CONCLUSION

During cell damage, cell thermogenesis has a linear correlation with intracellular energy. While during cell repair, there is a gradual saturation relationship between the temperature (small range) and ATP, which may be because the thermogenesis capacity of the cell is enhanced compared to conditions during cell energy storage. Additionally, there is an optimal drug concentration for cell action during cell injury and cell repair, which is not dose-dependent.

SIGNIFICANCE

Whether in inflammation production or treatment, there is an optimal drug concentration. The relationship between cell thermogenesis and intracellular energy reserves is related to cell processes. Quick analysis of the energy changes in different physiological process can be realized.

Multitargeted Feeding Strategies Improve Nutrition Outcome and Are Associated With Reduced Pneumonia in a Level 1 Trauma Intensive Care Unit

BACKGROUND

Factors impeding delivery of adequate enteral nutrition (EN) to trauma patients include delayed EN initiation, frequent surgeries and procedures, and postoperative ileus. We employed 3 feeding strategies to optimize EN delivery: (1) early EN initiation, (2) preoperative no nil per os feeding protocol, and (3) a catch-up feeding protocol. This study compared nutrition adequacy and clinical outcomes before and after implementation of these feeding strategies.

METHODS

All trauma patients aged ≥18 years requiring mechanical ventilation for ≥7 days and receiving EN were included. Patients who sustained nonsurvivable injuries, received parenteral nutrition, or were readmitted to the intensive care unit (ICU) were excluded. EN data were collected until patients received an oral diet or were discharged from the ICU. The improvement was quantified by comparing nutrition adequacy and outcomes between April 2014-May 2015 (intervention) and May 2012-June 2013 (baseline).

RESULTS

The intervention group (n = 118) received significantly more calories (94% vs 75%, P < .001) and protein (104% vs 74%, P < .001) than the baseline group (n = 121). The percentage of patients receiving EN within 24 and 48 hours of ICU admission increased from 41% to 70% and from 79% to 96% respectively after intervention (P < .001). Although there were fewer 28-ay ventilator-free days in the intervention group than in the baseline group (12 vs 16 days, P = .03), receipt of the intervention was associated with a significant reduction in pneumonia (odds ratio, 0.53; 95% confidence interval, 0.31-0.89; P = .017) after adjusting sex and Injury Severity Score.

CONCLUSIONS

Implementation of multitargeted feeding strategies resulted in a significant increase in nutrition adequacy and a significant reduction in pneumonia.

Comparison of sepsis rats induced by caecal ligation puncture or Staphylococcus aureus using a LC-QTOF-MS metabolomics approach

Sepsis is a whole-body inflammatory response to infection with high mortality and is treated in intensive care units (ICUs). In the present study, to identify metabolic biomarkers that can differentiate sepsis models induced by caecal ligation puncture (CLP) or Staphylococcus aureus (S. aureus), small molecular metabolites in the serum were measured by liquid chromatography quadruple time-of-flight mass spectrometry (LC-QTOF-MS) and analysed using the multivariate statistical analysis (MVA) of partial least square-discrimination analysis (PLS-DA) method. The results demonstrated that the body showed obvious metabolic disorders in the sepsis groups compared with the control group. A total of 8 potential biomarkers were identified in the CLP group, and 10 potential biomarkers were identified in the S. aureus group. These potential biomarkers primarily reflected an energy metabolism disorder, inflammatory response, oxidative stress and tissue damage, which occur during sepsis, and these markers might potentially be used to differentiate CLP from Staphylococcus aureus sepsis.

Haematological and febrile response to Escherichia coli lipopolysaccharide in 12-week-old cockerels of genetically diverse layer lines fed diets with increasing L-arginine levels

Due to its decisive function in the avian metabolic, endocrine and immune system L-arginine (Arg) is dietary indispensable for chickens. In 12-week-old cockerels of two high- and two low-performing purebred layer lines, the effects of increasing dietary Arg on the haematological and febrile response were studied over 48 h after single lipopolysaccharide (LPS) injection. The offered diets contained Arg equivalent to 70%, 100% and 200% of recommended supply. Pathophysiological alterations in weight gain, feed intake, body temperature and differential blood count were examined in comparison with their physiological initial values. Within the first 24 h after LPS injection, cockerels reduced feed intake and lost body weight subsequently. Thereby, low-performing genotypes lost body weight to a lesser extent than high-performing ones. The loss of body weight was further intensified by deficient dietary Arg. Within the following 24 h, cockerels recovered by improving feed intake and weight gain. Furthermore, LPS induced genotype-specific fever response: both brown genotypes showed initial hypothermia followed by longer lasting moderate hyperthermia, whereas the white genotypes exhibited biphasic hyperthermia. Fever response was accompanied by significant changes in differential blood counts. Characterized by lymphopenia and heterophilia, a severe leucopenia was observed from 4 to 8 h after LPS injection and replaced by a marked leucocytosis with longer lasting monocytosis up to 48 h after LPS injection. Under given pathophysiological conditions, deficiently Arg-supplied cockerels showed higher total leucocyte counts than adequately and excessively Arg-supplied cockerels. However, deficient and surplus dietary Arg tended to cause higher ratios between heterophils and lymphocytes. To conclude, present results confirmed that LPS induced numerous immunological changes in 12-week-old cockerels and emphasized that chicken's genotype is a source of variation to be considered for immunological studies. Deficient dietary Arg intensified acute changes in differential blood counts and weight gain during LPS-induced inflammation.

The impact of abdominal aortic aneurysm on muscle mass and energy expenditure: A novel preliminary investigation

OBJECTIVE

Vascular surgical patients, including those with abdominal aortic aneurysm (AAA), are nutritionally vulnerable. The aim of this study was to compare resting energy expenditure (REE) of patients with AAA relative to age- and gender-matched controls and explore relationships between aneurysm size and muscle mass.

METHODS

Twenty patients with AAA underwent assessment of REE using indirect calorimetry. Mid-arm circumference and triceps skinfold thickness were measured and corrected arm muscle area calculated. Twenty gender- and age-matched controls were assessed using the same procedures.

RESULTS

Mean (SD) age of participants with AAA was 74.7 (7.7) years, size of AAA ranged from 45 to 70 mm. Median (IQR) REE was significantly higher than controls [5990 (5469, 7017) kJ/day versus 5086 (4536, 5886) kJ/day, p = .011; or 69 (64, 80) kJ/kg/day versus 66 (61, 69) kJ/kg/day, p = .046]. While weight-adjusted REE was independent of aneurysm size (r = .200; p = .397), as aneurysm size increased, weight-adjusted corrected arm muscle area decreased (r = -.576; p = .008).

CONCLUSION

The raised REE and decline in muscle mass associated with larger AAA suggest that early detection and attention to nutritional requirements of patients with AAA may be warranted.

Prolonged induced hypothermia in hemorrhagic shock is associated with decreased muscle metabolism: a nuclear magnetic resonance-based metabolomics study

Hemorrhagic shock is a leading cause of trauma-related death in war and is associated with significant alterations in metabolism. Using archived serum samples from a previous study, the purpose of this work was to identify metabolic changes associated with induced hypothermia in a porcine model of hemorrhagic shock. Twelve Yorkshire pigs underwent a standardized hemorrhagic shock and resuscitation protocol to simulate battlefield injury with prolonged evacuation to definitive care in cold environments. Animals were randomized to receive either hypothermic (33°C) or normothermic (39°C) limited resuscitation for 8 h, followed by standard resuscitation. Proton nuclear magnetic resonance spectroscopy was used to evaluate serum metabolites from these animals at intervals throughout the hypothermic resuscitation period. Animals in the hypothermic group had a significantly higher survival rate (P = 0.02) than normothermic animals. Using random forest analysis, a difference in metabolic response between hypothermic and normothermic animals was identified. Hypothermic resuscitation was characterized by decreased concentrations of several muscle-related metabolites including taurine, creatine, creatinine, and amino acids. This study suggests that a decrease in muscle metabolism as a result of induced hypothermia is associated with improved survival.

Energy estimation and measurement in critically ill patients

The estimation of caloric needs of critically ill patients is usually based on energy expenditure (EE), while current recommendations for caloric intake most often rely on a fixed amount of calories. In fact, during the early phase of critical illness, caloric needs are probably lower than EE, as a substantial proportion of EE is covered by the non-inhibitable endogenous glucose production. Hence, the risk of overfeeding is higher during the early phase than the late phase, while the risk of underfeeding is higher during the late phase of critical illness. Therefore, an accurate measurement of EE can be helpful to prevent early overfeeding and late underfeeding. Available techniques to assess EE include predictive equations, calorimetry, and doubly labeled water, the reference method. The available predictive equations are often inaccurate, while indirect calorimetry is difficult to perform for several reasons, including a shortage of reliable devices and technical limitations. In this review, the authors intend to discuss the different techniques and the influence of the method used on the interpretation of the results of clinical studies.

Relationship between C-reactive protein, systemic oxygen consumption, and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) is known to result in elevated systemic oxygen consumption (Vo(2)) and increases in high-sensitivity C-reactive protein (hsCRP), although the relationship among hsCRP, Vo(2), and delayed cerebral ischemia (DCI) after SAH remains unknown. We hypothesized that hsCRP is directly associated with Vo(2) and that elevated Vo(2) is a predictor of DCI after SAH.

METHODS

Prospective serial assessments of Vo(2) and hsCRP over 4 prespecified time periods during the first 14 days after bleed in consecutive SAH patients admitted to a single academic medical center for a 2-year period.

RESULTS

One hundred ten SAH patients met study criteria (mean age, 55±16 years; 62% women), with a median admission Hunt Hess grade of 3 (interquartile range, 2-4). In multivariate generalized estimating equation model of the first 14 days after bleed, Vo(2) was associated with younger age (P=0.01), male gender (P=0.01), and hsCRP levels (P=0.03). Twenty-four (22%) patients had DCI develop, with a median onset on day 7 after bleed (interquartile range, 5-11). The mean Vo(2) (291±65 mL/min versus 226±55 mL/min; P=0.003) was higher in DCI patients. In a multivariable Cox proportional hazards model, younger age (hazard ratio, 1.2 per 5 years; 95% CI, 1.1-1.3), a higher modified Fisher scale score (hazard ratio, 3.4 per 1-point increase; 95% CI, 1.7-6.9), and higher Vo(2) (HR, 1.2 per 50-mL/min increase; 95% CI, 1.1-1.3) were predictive of DCI.

CONCLUSIONS

Systemic oxygen consumption is associated with hsCRP levels in the first 14 days after SAH and is an independent predictor of DCI.

Parenteral amino acid intakes in critically ill children: a matter of convenience

BACKGROUND

Parenteral and enteral amino acid requirements for nutrition balance and function have not been defined in critically ill children or adults. In addition to playing a role in protein synthesis, amino acids trigger signaling cascades that regulate various aspects of fuel and energy metabolism and serve as precursors for important substrates. Amino acids can also be toxic. In this study, parenteral intakes of essential and nonessential amino acids (EAAs and NEAAs) supplied to critically ill children were assessed as an initial step for further studies aimed at establishing parenteral amino acid requirements.

METHODS

A retrospective review was conducted to assess intakes of parenteral amino acid for 116 critically ill children, and these intakes were compared with EAA intakes recommended by the Institute of Medicine. Because there are no recommended intakes for NEAA, NEAA intakes were compared with mixed muscle protein content in the older children and breast milk amino acid content in the infants.

RESULTS

Parenteral EAAs were provided in amounts that exceeded recommended intakes for healthy children, except for phenylalanine and methionine, which although excessive, were given in less generous amounts. NEAAs were supplied in lower or higher amounts than the content of mixed muscle proteins or breast milk. Parenteral amino acid formulas are limited in taurine, glutamine, and asparagine despite the fact that inflammatory/immune proteins are rich in these amino acids.

CONCLUSIONS

Amino acid composition of parenteral formulas is variable and lacks scientific support. Parenteral amino acid intakes should be based on measured requirements to maintain nutrition and functional balance and on knowledge of toxicity.

Daily injection of tumor necrosis factor-{alpha} increases hepatic triglycerides and alters transcript abundance of metabolic genes in lactating dairy cattle

To determine whether inflammation can induce bovine fatty liver, we administered recombinant bovine tumor necrosis factor-alpha (rbTNF) to late-lactation Holstein cows. Cows (n = 5/treatment) were blocked by feed intake and parity and randomly assigned within block to control (CON; saline), rbTNF at 2 microg/(kg.d), or pair-fed control (saline, intake matched) treatments. Treatments were administered once daily by subcutaneous injection for 7 d. Plasma samples were collected daily for analysis of glucose and FFA and a liver biopsy was collected on d 7 for triglyceride (TG) and quantitative RT-PCR analyses. Data were analyzed using treatment contrasts to assess effects of tumor necrosis factor-alpha (TNFalpha) and decreased feed intake. By d 7, feed intake of both rbTNF and pair-fed cows was approximately 15% less than CON (P < 0.01). Administration of rbTNF resulted in greater hepatic TNFalpha mRNA and protein abundance and 103% higher liver TG content (P < 0.05) without affecting the plasma FFA concentration. Hepatic carnitine palmitoyltransferase 1 transcript abundance tended to be lower (P = 0.09) and transcript abundance of fatty acid translocase and 1-acyl-glycerol-3-phosphate acyltransferase was higher (both P < 0.05) after rbTNF treatment, consistent with increased FFA uptake and storage as TG. Transcript abundance of glucose-6-phosphatase (P < 0.05) and phosphoenolpyruvate carboxykinase 1 (P = 0.09), genes important for gluconeogenesis, was lower for rbTNF-treated cows. These findings indicate that TNFalpha promotes liver TG accumulation and suggest that inflammatory pathways may also be responsible for decreased glucose production in cows with fatty liver.

Improvement of Glucose Control in the Intensive Care Unit: An Interdisciplinary Collaboration Study

Background Strict glycemic control in critically ill patients is challenging for both physicians and nurses.

Objectives To determine the effect of focused education of intensive care staff followed by implementation of a glucose control protocol.

Methods A prospective observational study in a medical intensive care unit in a university hospital. After intensive education of nurses and physicians, a glucose control protocol with a nurse-managed insulin therapy algorithm was developed and implemented. Every measured blood glucose value and insulin dose per hour and per day were documented in 36 patients before and 44 patients after implementation of the protocol.

Results Median blood glucose levels decreased after implementation of the protocol (133 vs 110 mg/dL; P &lt; .001). The amounts of time when patients’ blood glucose levels were less than 110 mg/dL and less than 150 mg/dL increased after implementation of the protocol (8% vs 44%; 75% vs 96%; P&lt;.001). The median use of insulin increased after implementation of the protocol (28 vs 35 IU/day; P=.002). Diabetic patients had higher median blood glucose levels than did nondiabetic patients both before (138 vs 131 mg/dL) and after (115 vs 108 mg/dL; P&lt;.001) implementation, although median insulin use also increased (before implementation, 33 vs 26 IU/day; P=.04; after implementation, 46 vs 30 IU/day; P &lt; .001).

Conclusions Use of a collaboratively developed glucose control protocol led to decreased median blood glucose levels and to longer periods of normoglycemia. Despite increased insulin use, glucose control was worse in diabetic patients.

Resting energy expenditure and its determinants in hemodialysis patients

OBJECTIVE

Chronic kidney disease is associated with several metabolic disturbances that can affect energy metabolism. As resting energy expenditure (REE) is scarcely investigated in patients on hemodialysis (HD) therapy, we aimed to evaluate the REE and its determinants in HD patients.

DESIGN

Cross-sectional study.

SETTING

Dialysis Unit of the Nephrology Division, Federal University of São Paulo, Brazil.

SUBJECTS

The study included 55 patients (28 male, 41.4+/-12.6 years old) undergoing HD therapy thrice weekly for at least 2 months, and 55 healthy individuals pair matched for age and gender. Subjects underwent fasting blood tests, as well as nutritional assessment, and the REE was assessed by indirect calorimetry.

RESULTS

REE of HD patients was similar to that of pair-matched controls (1379+/-272 and 1440+/-259 kcal/day, respectively), even when adjusted for fat-free mass (P=0.24). REE of HD patients correlated positively with fat-free mass (r=0.74; P<0.001) and body mass index (r=0.37; P<0.01), and negatively with dialysis adequacy (r=-0.46; P<0.001). No significant univariate correlation was found between REE and age, dialysis vintage, serum creatinine, urea, albumin, bicarbonate, parathyroid hormone (PTH) or high-sensitivity C-reactive protein (CRP). In the multiple linear regression analysis, using REE as dependent variable, the final model showed that besides the well-recognized determinants of REE such as fat-free mass and age, PTH and CRP were the independent determinants of REE in HD patients (R (2)=0.64).

CONCLUSIONS

In this study, the REE of HD patients was similar to that of healthy individuals, even with the positive effect of secondary hyperparathyroidism and inflammation on REE of these patients.

Weight-adjusted resting energy expenditure is not constant in critically ill patients

OBJECTIVE

In critically ill patients, energy requirements are frequently calculated as a multiple of total body weight presuming a linear relationship between total body weight and resting energy expenditure (REE); however, it is doubtful if this estimation of energy needs should be applied to all patients, particularly to overweight patients, since adipose tissue has a low contribution to REE. This study was undertaken to test the hypothesis that REE adjusted for total body weight decreases with increasing body mass index in critically ill patients. Additionally, measured REE was compared with three predictive equations.

DESIGN AND SETTING

Clinical study in a university hospital intensive care unit.

PATIENTS

One hundred critically ill patients admitted to the intensive care unit.

MEASUREMENTS AND RESULTS

Patients were included into four groups according to their body mass index (normal weight, pre-obese, obese, and morbidly obese). Measured REE was assessed using indirect calorimetry. Energy needs were calculated using the basal metabolic rate, the Consensus Statement of the American College of Chest Physicians (REEacs), and 25[Symbol: see text]kcal/kg of ideal body weight (REEibw). Adjusted REE was 24.8 +/- 5.5 kcal/kg in normal weight, 22.0 +/- 3.7 kcal/kg in pre-obese, 20.4 +/- 2.6 kcal/kg in obese, and 16.3 +/- 2.3 kcal/kg in morbidly obese patients (p < 0.01). Basal metabolic rate underestimated measured REE in normal weight and pre-obese patients. REEacs and REEibw over- and underestimated measured REE in overweight patients, respectively.

CONCLUSIONS

Predictive equations were not able to estimate measured REE adequately in all the patients. Adjusted REE decreased with increasing body mass index; thus, a body mass index group-specific adaptation for the estimation of energy needs should be applied.

Physiological concentrations of insulin induce endothelin-dependent vasoconstriction of skeletal muscle resistance arteries in the presence of tumor necrosis factor-alpha dependence on c-Jun N-terminal kinase

OBJECTIVE

Tumor necrosis factor-alpha (TNF-alpha) has been linked to obesity-related insulin resistance and impaired endothelium-dependent vasodilatation, but the mechanisms have not been elucidated. To investigate whether TNF-alpha directly impairs insulin-mediated vasoreactivity in skeletal muscle resistance arteries and the role of c-Jun N-terminal kinase (JNK) in this interference.

METHODS AND RESULTS

Insulin-mediated vasoreactivity of isolated resistance arteries of the rat cremaster muscle to insulin (4 to 3400 microU/mL) was studied in the absence and presence of TNF-alpha (10 ng/mL). Although insulin or TNF-alpha alone did not affect arterial diameter, insulin induced dose-dependent vasoconstriction of cremaster resistance arteries in the presence of TNF-alpha, (-12+/-1% at 272 microU/mL). Blocking endothelin receptors in the absence of TNF-alpha uncovered insulin-mediated vasodilatation (18+/-6% at 272 microU/mL) but not in the presence of TNF-alpha (2+/-2% at 272 microU/mL), showing that TNF-alpha inhibits vasodilator effects of insulin. Using digital imaging microscopy, we discovered that TNF-alpha activates JNK in arterial endothelium, visible as an increase in phosphorylated JNK. Moreover, inhibition of JNK with the cell-permeable peptide inhibitor L-JNKI abolished insulin-mediated vasoconstriction in the presence of TNF-alpha, showing that JNK is required for interaction between TNF-alpha and insulin.

CONCLUSIONS

TNF-alpha inhibits vasodilator but not vasoconstrictor effects of insulin in skeletal muscle resistance arteries, resulting in insulin-mediated vasoconstriction in the presence of TNF-alpha. This effect of TNF-alpha is critically dependent on TNF-alpha-mediated activation of JNK.

Inflammation is associated with increased energy expenditure in patients with chronic kidney disease

BACKGROUND

Inflammation, a clinical condition observed in patients with chronic kidney disease (CKD), may be related to increased resting energy expenditure (REE).

OBJECTIVES

The main objective was to investigate the relation between inflammation and REE in patients with CKD who are not undergoing dialysis. We also aimed to analyze whether a decrease in C-reactive protein (CRP) would result in a reduction in REE.

DESIGN

This study enrolled 132 patients with CKD who were not undergoing dialysis, who had creatinine clearance from 5 to 65 mL.min(-1).1.73 m(-2), and who were 53.6 +/- 16 y old; 82 (62.1%) were men. Twenty-nine patients had clinical signs of infection. REE was measured by using indirect calorimetry, and inflammation was evaluated by using high-sensitivity CRP measurement. Patients were divided according to tertiles of CRP with the following intertertile ranges: first tertile, CRP < or = 0.14 mg/dL (n = 43); second tertile, CRP 0.15-0.59 mg/dL (n = 46); and third tertile, CRP > or = 0.60 mg/dL (n = 43). REE was measured before and after treatment in 10 patients who had inflammation or infection.

RESULTS

After adjustment for age, sex, and lean body mass, the REE of the third (1395 kcal/d; P = 0.02) and second (1355 kcal/d; P = 0.04) tertiles was significantly higher than that of the first tertile (1286 kcal/d). In the multiple linear regression analysis (n = 132), the independent determinants of REE were lean body mass, CRP, and age (R2 = 0.55). After treatment of infection in a subgroup of 10 patients, it was observed that a significant reduction in CRP concentration was accompanied by a significant reduction of 174 +/- 165 kcal that accounted for 13% of the initial REE.

CONCLUSION

This study showed that inflammation is associated with increased REE in patients with CKD.

Immune response, not immune maintenance, is energetically costly in wild white-footed mice (Peromyscus leucopus)

Understanding the cost of immune function is essential for more accurate characterization of energy budgets of animals and better understanding of the role of immunity in the evolution of life-history strategies. We examined the energetic cost of maintaining a normally functioning immune system and mounting a mild immune response in wild male white-footed mice (Peromyscus leucopus). To evaluate the cost of maintaining immunocompetence, we compared resting and daily metabolic rates (RMR; DMR) and masses of body organs of mice whose immune systems were suppressed by cyclophosphamide with those of control mice. To evaluate the cost of mounting an immune response, we measured RMR, DMR, and organ masses in mice whose humoral and cell-mediated immune responses had been stimulated by injections of sheep red blood cells and phytohemagglutinin, respectively. Immunosuppression resulted in a significant reduction in circulating leukocytes, by 225%, but no significant effect on metabolic rates or organ masses. Immunochallenged animals showed no significant differences in metabolic rates compared with control animals but did exhibit significantly smaller dry masses of the small intestine and testes, by 74% and 22%, respectively. We concluded that the cost of maintaining the immune system was minimal. In contrast, there was a significant energetic cost of mounting an immune response that, depending on its magnitude, can be met through reductions in energy allocation to other physiological systems.

Tumor Necrosis Factor-α Inhibits Insulin’s Stimulating Effect on Glucose Uptake and Endothelium-Dependent Vasodilation in Humans

Background— Inflammatory mechanisms could be involved in the pathogenesis of both insulin resistance and atherosclerosis. Therefore, we aimed at examining whether the proinflammatory cytokine tumor necrosis factor (TNF)-α inhibits insulin-stimulated glucose uptake and insulin-stimulated endothelial function in humans.

Methods and Results— Healthy, lean male volunteers were studied. On each study day, 3 acetylcholine (ACh) or sodium nitroprusside (SNP) dose-response studies were performed by infusion into the brachial artery. Before and during the last 2 dose-response studies, insulin and/or TNF-α were coinfused. During infusion of insulin alone for 20 minutes, forearm glucose uptake increased by 220±44%. This increase was completely inhibited during coinfusion of TNF-α (started 10 min before insulin) with a more pronounced inhibition of glucose extraction than of blood flow. Furthermore, TNF-α inhibited the ACh forearm blood flow response ( P <0.001), and this inhibition was larger during insulin infusion ( P =0.01) but not further increased by N G -monomethyl- l -arginine acetate ( P =0.2). Insulin potentiated the SNP response less than the ACh response and the effect of TNF-α was smaller ( P <0.001); TNF-α had no effect on the SNP response without insulin infusion. Thus, TNF-α inhibition of the combined response to insulin and ACh was likely mediated through inhibition of NO production.

Conclusion— These results support the concept that TNF-α could play a role in the development of insulin resistance in humans, both in muscle and in vascular tissue.

Does the oxidative/glycolytic ratio determine proliferation or death in immune recognition?

Here we discuss the possibility that the way cells utilize fuel(s) for energy confers the properties that can be recognized by the immune system and, reciprocally, that recognition by the immune system can alter the balance of the cell's energy metabolism. We propose that immune recognition, of somatic cells via MHC can alter the their energy metabolism and induce a metabolic shift. We demonstrate the reciprocal relationship that inducing a shift in metabolism toward glycolysis by supplying glucose and insulin results in the upregulation of immunologically recognizable molecules such as cell surface Fas. Thus, immune recognition can induce metabolic deviation. Metabolic deviation can result in altered immune recognition and ultimately in cell proliferation, cell differentiation, or cell death.

Energy expenditure measurements in ventilated critically ill children: within- and between-day variability

BACKGROUND

Energy expenditure measurement (EEM) by indirect calorimetry is used as a research and clinical tool in pediatric intensive care units. The aims of the study were to determine if a 30-minute EEM is representative of a 24-hour EEM (within-day variation); to determine if there is any diurnal variation during the 24-hour period of EEM; and to determine if there is a clinically significant between day variation of EEMs.

METHODS

To determine within-day variation, energy expenditure was measured for a period of 24 hours for each subject (n = 11). The 24-hour period was then divided into 30-minute periods. The 30-minute means were compared with the 24-hour means. To determine between-day variation, EEMs were made daily for 30 minutes.

RESULTS

In the within-day study, the overall mean percent coefficient of variation of the 30-minute measurements was 7.2% +/- 4.5%. There was no significant difference between the 30-minute means and the 24-hour means for each patient (p < .691). In 8 subjects the 30-minute means did not differ from the 24-hour mean by more than 20%. No diurnal variation was observed. The mean percent variation of between day EEM was 21% +/- 16%; the range was 1% to 69%.

CONCLUSION

In critically ill ventilated children, clinically relevant within-day variations in EEM are uncommon and a single 30-minute EEM gives an acceptable guide to the level of nutrition support required. Between-day variations can, however, be large and daily EEMs are required.

Cytokine-induced glucose uptake in skeletal muscle: redox regulation and the role of alpha-lipoic acid

In L6 myotubes, glucose uptake stimulated by interferon (IFN)-gamma or lipopolysaccharides (LPS) and a combination of LPS, IFN-gamma, and tumor necrosis factor (TNF)-alpha was inhibited by the antioxidant pyrrolidinedithiocarbamate and potentiated in reduced glutathione (GSH)-deficient cells. Also, the stimulatory effect of LPS and IFN-gamma individually, and of a combination of LPS, IFN-gamma, and TNF-alpha, on glucose uptake was associated with an increased level of intracellular oxidants (dichlorofluorescein assay) and loss of intracellular GSH. Study of the individual effects of LPS, IFN-gamma, and TNF-alpha as well as of a combination of the three activators provided evidence against a role of nitric oxide in mediating the stimulatory effect of the above-mentioned agents on glucose uptake. We also observed that the insulin-mimetic nutrient alpha-lipoic acid (LA; R-enantiomer) is able to stimulate glucose uptake in cytokine-treated cells that are insulin resistant. This study shows that cytokine-induced glucose uptake in skeletal muscle cells is redox sensitive and that, under conditions of acute infection that is accompanied with insulin resistance, LA may have therapeutic implications in restoring glucose availability in tissues such as the skeletal muscle.

From malnutrition to refeeding during anorexia nervosa

Anorexia nervosa is one of the most common forms of malnutrition observed in Western society in individuals without physical diseases, with an average risk of mortality of 20% in a younger population aged between 15 and 25 years. It is characterised by an initial dramatic decrease in food intake that leads to profound depletion in muscle and fat mass. During the course of the disease, the resting energy expenditure decreases proportionally to the loss of lean body mass with a decrease in thyroid hormone secretion. The metabolic adaptation during anorexia nervosa is similar to that observed during starvation with a relative sparing of protein stores. After an initial weight loss, the total energy expenditure is similar to that in normal individuals, with a decrease in resting energy expenditure and an increased energy-related physical activity. At the end stage of wasting, however, physical activity dramatically decreases as well as energy intake. This metabolic adaptation of semi-starvation is impaired during refeeding with an increase in the thermic effect of food and a high risk of refeeding syndrome with severe hypophosphatemia.

Fasting in healthy individuals and adaption to undernutrition during chronic disease

During long-term fasting, gluconeogenesis from amino acids was thought to lessen, when ketone bodies from lipolysis became a major fuel source. Thus, muscle mass is conserved. However, recent studies show that this adaptation does not occur in chronic undernourishment. In cancer, chronic undernutrition without disease, and HIV infection, carbohydrate utilization is high. Enhanced hepatic glucose production occurs in active inflammatory bowel disease and in underweight cancer patients. Repletion of tissue after undernutrition is energetically inefficient because of enhanced diet induced thermogenesis (following anorexia nervosa) and decreased fat, and increased protein, oxidation (in tuberculosis).