The metabolic basis of the increase of the increase in energy expenditure in severely burned patients

Challenges in the Management of Large Burns

Large burns provoke profound pathophysiological changes. Survival rates of patients with large burns have improved significantly with the advancement of critical care and adaptation of early excision protocols. Nevertheless, care of large burn wounds remains challenging secondary to limited donor sites, prolonged time to wound closure, and immunosuppression. The development of skin substitutes and new grafting techniques decreased time to wound closure. Individually, these methods have limited success, but a combination of them may yield more successful outcomes. Early identification of patients with likely poor prognosis should prompt goals of care discussion and involvement of a palliative care team when possible.

Large area fractional laser treatment of mouse skin increases energy expenditure

Fractional laser (FL) treatment is a common dermatologic procedure that generates arrays of microscopic treatment zones separated by intact tissue, promoting fast wound healing. Using a mouse model, we introduced a large area fractional laser treatment (LAFLT) method to study metabolic effects. Using two laser modalities, ablative FL (AFL) and non-ablative FL (NAFL), and exposing different percentages of mice's total body surface area (TBSA), we followed changes in metabolic parameters in real time using metabolic cages. Additionally, body composition, markers of inflammation, neurohormonal signaling, and browning of adipocytes were investigated. LAFLT, especially in high TBSA groups, had specific metabolic effects such as significantly increased average daily energy expenditure, increased fat mass loss, systemic browning of adipocytes, and inflammatory states, without compromising other organs. The ability of LAFLT to stimulate metabolism in a controlled way could develop into a promising therapeutic treatment to induce positive metabolic changes that replace or augment systemic drugs.

Burns: Classification, Pathophysiology, and Treatment: A Review

Burns and their treatment are a significant medical problem. The loss of the physical barrier function of the skin opens the door to microbial invasion and can lead to infection. The repair process of the damage caused by the burn is impaired due to the enhanced loss of fluids and minerals through the burn wound, the onset of hypermetabolism with the concomitant disruption of nutrient supply, and derangements in the endocrine system. In addition, the initiated inflammatory and free radical processes drive the progression of oxidative stress, the inhibition of which largely depends on an adequate supply of antioxidants and minerals. Clinical experience and research provide more and more data to make the treatment of patients with thermal injury increasingly effective. The publication discusses disorders occurring in patients after thermal injury and the methods used at various stages of treatment.

Murine scald models characterize the role of neutrophils and neutrophil extracellular traps in severe burns

Introduction

Severe burns cause unique pathophysiological alterations especially on the immune system. A murine scald model was optimized as a basis for the understanding of immunological reactions in response to heat induced injury. The understanding of the roles of neutrophil extracellular traps (NETs) and DNases will support the development of new surgical or pharmacological strategies for the therapy of severe burns.

Methods

We studied C57BL/6 mice (n=30) and employed four scalding protocols with varying exposure times to hot water. An additional scald group with a shorter observational time was generated to reduce mortality and study the very early phase of pathophysiology. At 24h or 72h, blood was drawn and tissue (wound, liver, lung, spleen) was analyzed for the presence of NETs, oxidative stress, apoptosis, bacterial translocation, and extracellular matrix re-organization. In addition, we analyzed the transcriptome from lung and liver tissues.

Results

Exposure to hot water for 7s led to significant systemic and local effects and caused considerable late mortality. Therefore, we used an observation time of 24h in this groups. To study later phases of burns (72h) an exposure time of 6s is optimal. Both conditions led to significant disorganization of collagen, increased oxidative stress, NET formation (by immunodetection of H3cit, NE, MPO), apoptosis (cC3) and alterations of the levels of DNase1 and DNase1L3. Transcriptome analysis revealed remarkable alterations in genes involved in acute phase signaling, cell cohesion, extracellular matrix organization, and immune response.

Conclusion

We identified two scald models that allow the analysis of early (24h) or late (72h) severe burn effects, thereby generating reproducible and standardized scald injuries. The study elucidated the important involvement of neutrophil activity and the role of NETs in burns. Extensive transcriptome analysis characterized the acute phase and tissue remodeling pathways involved in the process of healing and may serve as crucial basis for future in-depth studies.

Pathological changes in the brain after peripheral burns

Brain injuries are common complications in patients with thermal burns and are associated with unpleasant outcomes. In clinical settings, it was once believed that brain injuries were not major pathological processes after burn, at least in part due to the unavailability of specific clinical manifestations. Burn-related brain injuries have been studied for more than a century, but the underlying pathophysiology has not been completely clarified. This article reviews the pathological changes in the brain following peripheral burns at the anatomical, histological, cytological, molecular and cognitive levels. Therapeutic indications based on brain injury as well as future directions for research have been summarized and proposed.

Modulation of Burn Hypermetabolism in Preclinical Models

Severe burns elicit a state of physiological stress and increased metabolism to help the body compensate for the changes associated with the traumatic injury. However, this hypermetabolic state is associated with increased insulin resistance, cardiovascular dysfunction, skeletal muscle catabolism, impaired wound healing, and delayed recovery. Several interventions were attempted to modulate burn hypermetabolism, including nutritional support, early excision and grafting, and growth hormone application. However, burn hypermetabolism still imposes significant morbidity and mortality in burn patients. Due to the limitations of in vitro models, animal models are indispensable in burn research. Animal models provide researchers with invaluable tools to test the safety and efficacy of novel treatments or advance our knowledge of previously utilized agents. Several animal studies evaluated novel therapies to modulate burn hypermetabolism in the last few years, including recombinant human growth hormone, erythropoietin, acipimox, apelin, anti-interleukin-6 monoclonal antibody, and ghrelin therapies. Results from these studies are promising and may be effectively translated into human studies. In addition, other studies revisited drugs previously used in clinical practice, such as insulin and metformin, to further investigate their underlying mechanisms as modulators of burn hypermetabolism. This review aims to update burn experts with the novel therapies under investigation in burn hypermetabolism with a focus on applicability and translation. Furthermore, we aim to guide researchers in selecting the correct animal model for their experiments by providing a summary of the methodology and the rationale of the latest studies.

Lytic cocktail: An effective method to alleviate severe burn induced hyper-metabolism through regulating white adipose tissue browning

Background

Browning of white adipose tissue is associated with elevated resting metabolic rates and is considered to be one of the indispensable causes of hypermetabolism in burn patients. Hypermetabolism means increased resting energy expenditure, raised body temperature and acute-phase proteins. Persistently elevated levels of circulating stress hormones have been reported to induce browning of subcutaneous white adipose tissue. The lytic cocktail is a combination of medicines pethidine, chlorpromazine, and promethazine that has been used clinically in sedation for the management of patients. As reported this sedative treatment can reduce the expression of catecholamines in major burn rats. Thus, in this paper we focused on the effects of lytic cocktail in the regulation of white adipose tissue browning and hypermetabolism and we further investigated the underlying mechanism.

Methods

A 30% total body surface area (TBSA) Ⅲ degree scald rat model was used for this study. The rats were randomly divided into a sham scald group, a scalding with immediate resuscitation group, and a group of scalding with immediate resuscitation and lytic cocktail treatment. The levels of norepinephrine and epinephrine in plasma were dynamically detected. Changes of the rat body weight and food intake were recorded and compared as indexes of metabolism responses after post-scalding. For the study of white adipose tissue browning, inguinal adipose tissue was used. Metabolic changes, while indicatives of white fat browning were measured by PET/CT. The expression of white adipose browning related proteins and the changes of mitochondria number were used to assess browning of inguinal adipose.

Results

The level of plasma catecholamines norepinephrine and epinephrine in the lytic cocktail-treated group was significantly lower than the other two groups. Morphology and PET/CT showed that the inguinal white adipose browning was inhibited in the lytic cocktail treated group, whereas scalding with immediate resuscitation group showed browning of white adipose. The number of mitochondria, the expressions of white adipose browning related proteins in the lytic cocktail group were also significantly lower than that of the group of scalding with immediate resuscitation.

Conclusion

By reducing expression of heat-related proteins, the application of lytic cocktail medicines inhibits the white adipose tissue browning, which suppresses hypermetabolism in scalded rats. The mechanism might be related to decreased expression levels of stress hormones induced by lytic cocktail. This research suggests that lytic cocktails may be an effective treatment for hypermetabolism after severe burn injury.

Burn-induced hypermetabolism and skeletal muscle dysfunction

Critical illnesses, including sepsis, cancer cachexia, and burn injury, invoke a milieu of systemic metabolic and inflammatory derangements that ultimately results in increased energy expenditure leading to fat and lean mass catabolism. Burn injuries present a unique clinical challenge given the magnitude and duration of the hypermetabolic response compared with other forms of critical illness, which drastically increase the risk of morbidity and mortality. Skeletal muscle metabolism is particularly altered as a consequence of burn-induced hypermetabolism, as it primarily provides a main source of fuel in support of wound healing. Interestingly, muscle catabolism is sustained long after the wound has healed, indicating that additional mechanisms beyond wound healing are involved. In this review, we discuss the distinctive pathophysiological response to burn injury with a focus on skeletal muscle function and metabolism. We first examine the diverse consequences on skeletal muscle dysfunction between thermal, electrical, and chemical burns. We then provide a comprehensive overview of the known mechanisms underlying skeletal muscle dysfunction that may be attributed to hypermetabolism. Finally, we review the most promising current treatment options to mitigate muscle catabolism, and by extension improve morbidity and mortality, and end with future directions that have the potential to significantly improve patient care.

Effect of Mitochondrial Antioxidant (Mito-TEMPO) on Burn-Induced Cardiac Dysfunction

BACKGROUND

Imbalance of oxidants/antioxidants results in heart failure, contributing to mortality after burn injury. Cardiac mitochondria are a prime source of reactive oxygen species (ROS), and a mitochondrial-specific antioxidant may improve burn-induced cardiomyopathy. We hypothesize that the mitochondrial-specific antioxidant, Triphenylphosphonium chloride (Mito-TEMPO), could protect cardiac function after burn.

STUDY DESIGN

Male rats had a 60% total body surface area (TBSA) scald burn injury and were treated with/without Mito-TEMPO (7 mg/kg-1, intraperitoneal) and harvested at 24 hours post-burn. Echocardiography (ECHO) was used for measurement of heart function. Masson Trichrome and hematoxylin and eosin (H & E) staining were used for cardiac fibrosis and immune response. Qualitative polymerase chain reaction (qPCR) was used for mitochondrial DNA replication and gene expression.

RESULTS

Burn-induced cardiac dysfunction, fibrosis, and mitochondrial damage were assessed by measurement of mitochondrial function, DNA replication, and DNA-encoded electron transport chain-related gene expression. Mito-TEMPO partially improved the abnormal parameters. Burn-induced cardiac dysfunction was associated with crosstalk between the NFE2L2-ARE pathway, PDE5A-PKG pathway, PARP1-POLG-mtDNA replication pathway, and mitochondrial SIRT signaling.

CONCLUSIONS

Mito-TEMPO reversed burn-induced cardiac dysfunction by rescuing cardiac mitochondrial dysfunction. Mitochondria-targeted antioxidants may be an effective therapy for burn-induced cardiac dysfunction.

A prospective pilot study of the energy balance profiles in acute non-severe burn patients

BACKGROUND

Major burn patients have been shown to exhibit a hyper-metabolic state of activity which can persist for up to two years after burn. The relationship between total body surface area (TBSA) and resting metabolic rate (RMR) has been investigated in larger burns (≥20% TBSA), however not in non-severe burns (≤15% TBSA). The primary aim of this observational study was to examine the association between the acute effects of burns <15% TBSA with RMR in patients using indirect calorimetry, as well as any potential covariates. The secondary aim was to determine 24-h energy balance.

METHODS

The study included data from 39 participants (82% male), all admitted to the State Adult Burn Unit at Fiona Stanley Hospital. Each patient was recruited upon admission and RMR data was collected on day four (± one day) after burn.

RESULTS

The pooled data bivariate correlation showed a significant relationship between RMR and TBSA (r=0.435, p=0.009). A stronger relationship was also found between RMR and TBSA in males (r=0.634, p=0.001). Patients recorded a caloric deficit of 116kcal/day.

CONCLUSION

This study demonstrated that a moderately strong linear association exists between RMR and TBSA in males for burns of ≤15% TBSA. The energy balance data indicated that supplementation of calorific intake for non-severe burns suggests careful consideration.

The pathogenesis and diagnosis of sepsis post burn injury

Burn is an under-appreciated trauma that is associated with unacceptably high morbidity and mortality. Although the survival rate after devastating burn injuries has continued to increase in previous decades due to medical advances in burn wound care, nutritional and fluid resuscitation and improved infection control practices, there are still large numbers of patients at a high risk of death. One of the most common complications of burn is sepsis, which is defined as “severe organ dysfunction attributed to host's disordered response to infection” and is the primary cause of death in burn patients. Indeed, burn injuries are accompanied by a series of events that lead to sepsis and multiple organ dysfunction syndrome, such as a hypovolaemic state, immune and inflammatory responses and metabolic changes. Therefore, clear diagnostic criteria and predictive biomarkers are especially important in the prevention and treatment of sepsis and septic shock. In this review, we focus on the pathogenesis of burn wound infection and the post-burn events leading to sepsis. Moreover, the clinical and promising biomarkers of burn sepsis will also be summarized.

The Influence of Obesity on Treatment and Outcome of Severely Burned Patients

Obesity and the related medical, social, and economic impacts are relevant multifactorial and chronic conditions that also have a meaningful impact on outcomes following a severe injury, including burns. In addition to burn-specific difficulties, such as adequate hypermetabolic response, fluid resuscitation, and early wound coverage, obese patients also present with common comorbidities, such as arterial hypertension, diabetes mellitus, or nonalcoholic fatty liver disease. In addition, the pathophysiologic response to severe burns can be enhanced. Besides the increased morbidity and mortality compared to burn patients with normal weight, obese patients present a challenge in fluid resuscitation, perioperative management, and difficulties in wound healing. The present work is an in-depth review of the current understanding of the influence of obesity on the management and outcome of severe burns.

Bioelements in the treatment of burn injuries - The complex review of metabolism and supplementation (copper, selenium, zinc, iron, manganese, chromium and magnesium)

Appropriate nutrition is a key component of burn treatment and should be regarded as an integral part of the therapeutic process in burn patients. A nutritional intervention plan should not only allow for adequate quantities of energy and protein but also carefully consider the supply of macro- and micronutrients. As a result of the severe inflammatory response, oxidative stress, and hypermetabolic state, accompanied by often extensive exudation in burn patients, there is a considerable loss of macro- and micronutrients, including essential trace elements. This leads to certain complications, involving e.g. more frequent infections and impaired wound healing. Our current body of knowledge is still insufficient, and the studies carried out to date focus for the most part on the imbalances in trace elements, such as copper (Cu), selenium (Se), and zinc (Zn). Nevertheless, there are many other trace elements involved in immune functions, regulating gene expression or antioxidant defense, and many of those have not been properly investigated in a clinical setting. Due to the insufficient amount of unambiguous literature data and relatively few, often dated, studies carried out with small patient groups, further evaluation of macro- and microelements in burn patients seems indispensable, e.g. to bring up to date local nutritional protocols.

Brown adipose tissue recruitment in a rodent model of severe burns

BACKGROUND

Severe burns results in a prolonged hypermetabolic response. Brown adipose tissue (BAT), abundant in uncoupling protein 1 (UCP1), plays a key role in non-shivering thermogenesis. We set out to determine if BAT is recruited in response to severe burns.

METHODS

Male balb-c mice underwent scald burns on approximately 20-25% of their total body surface. BAT was harvested from the interscapular fat pad of sham and burned mice at 3h, 24h, 4 days, and 10 days after injury. High-resolution respirometry was used to determine mitochondrial respiratory function in BAT. BAT protein concentration, and mitochondrial enzyme activity were also determined.

RESULTS

Respiration increased in BAT of burned mice, peaking at 24h after injury (after injury, P<0.001). While UCP1 independent respiration was not significantly altered by burn, UCP1 dependent respiration increased >2-fold at 24h after injury when compared to the 3h and sham group (P<0.01). Normalized to citrate synthase activity, total uncoupled (P<0.05) and UCP1 dependent (P<0.01) respiration remained elevated at 24h after injury.

CONCLUSIONS

We show a time-dependent recruitment of rodent BAT in response to severe burns. Given recent reports that humans, including patients with severe burns, have functional BAT, these data support a role for BAT in the hypermetabolic response to severe burns.

Nutritional management of a kitten with thermal burns and septicaemia

Case summary

A 3-month-old entire female British Shorthair cat presented for further management of thermal burns after falling into a bath of scalding water. On presentation to the primary care clinician the kitten was obtunded, markedly painful and relatively bradycardic, consistent with a state of shock. The haircoat was wet, with erythematous skin and sloughing from the digital pads and anal mucosa. The primary care clinician administered opioid analgesia, sedation, antibiotics and started intravenous (IV) fluid therapy prior to referral. On arrival to the referral hospital the kitten was obtunded with respiratory and cardiovascular stability but was overtly painful and resistant to handling. The kitten required intensive management with IV and regional analgesia, IV broad-spectrum antibiosis, IV fluid therapy, enteral nutrition and wound management, including surgical debridement and topical antibiotic therapy. Septicaemia developed during the hospitalisation. Multidrug-resistant Escherichia coli and Pseudomonas aeruginosa were cultured, and antibiosis was escalated to IV imipenem. Acute respiratory distress syndrome was suspected following the development of dyspnoea. Early enteral nutrition within 24 h of admission was initiated using an oesophageal feeding tube and a veterinary therapeutic liquid diet. Over the ensuing 72 h the kitten started voluntary intake of food alongside oesophageal tube feeds. The kitten experienced continued weight loss despite the provision of nutritional support to meet, and then later exceed, the estimated resting energy requirements. Caloric intake was gradually increased to a total of 438% of the calculated resting energy requirement using the most recent daily body weight, eventually resulting in stabilisation of weight loss and weight gain.

Relevance and novel information

There is limited published information on the nutritional management of veterinary patients with thermal burn injury. Hypermetabolic states related to burn injuries are induced and maintained by complex interactions of catecholamines, stress hormones and inflammatory cytokines on proteolysis, lipolysis and glycogenolysis. Secondary infections are common following burn injury and the subsequent proinflammatory state perpetuates hypermetabolism and catabolism. These states present a challenge in both predicting and providing adequate nutrition, particularly in a paediatric septic patient. This subset of patients should be monitored closely during hospitalisation to ensure body weight and condition are maintained (while taking into consideration hydration status), and caloric intake is adjusted accordingly to meet nutritional support goals. Extensive research exists regarding the nutritional requirements and metabolic derangements of people with thermal burns. However, the importance of maintaining body weight and body condition in veterinary burn patients, and the association between nutritional support and reduced morbidity and mortality, has not been investigated and remains to be elucidated.

Prospective Study on Energy Expenditure in Patients With Severe Burns

BACKGROUND

Nutrition therapy is recognized as one of the most significant treatment aspects for burn patients. However, data were limited regarding the actual nutrition practices in patients with severe burn injury. This study aims to explore the measured energy expenditure (MEE) changes in severe burn patients and to evaluate the precision of commonly used predictive formulas for estimating predictive energy expenditure (PEE) in burn patients.

METHODS

A prospective multicenter trial was conducted in the intensive care units in the hospitals enrolling the severely burned patients. Data on MEE and PEE were collected and analyzed.

RESULTS

Forty-three patients were enrolled from 3 hospitals. All the patients had severe burns. MEE was measured by metabolic cart, and the MEE on the seventh day after severe burns was as high as 65 kcal/kg, which was 267% of the basal metabolic rate. The presence of hypermetabolism was sustained throughout the 21-day afterburn and decreased gradually to 34 kcal/kg thereafter until 4 weeks after injury. Wound percentage after skin-grafting therapy, time course of burn injury, the existence of severe sepsis, and blood infection were significantly associated with higher MEE. Compared with PEE and MEE, Toronto formula could estimate patients' energy requirements with more accuracy; Curreri and Pennisi formula both significantly overestimated the patient's energy expenditure, whereas underestimation occurred with the Harris-Benedict formula.

CONCLUSIONS

Severe burn patients were hypermetabolic at the early stage and sustained this status over a long time. The Toronto formula was the unbiased method to predict energy expenditure.

The Link between Hypermetabolism and Hypernatremia in Severely Burned Patients

Hypernatremia is common in critical care, especially in severely burned patients. Its occurrence has been linked to increased mortality. Causes of hypernatremia involve a net gain of sodium or a loss of free water. Renal loss of electrolyte-free water due to urea-induced osmotic diuresis has been described as causative in up to 10% of hypernatremic critical ill patients. In this context, excessive urea production due to protein catabolism acts as major contributor. In severe burn injury, muscle wasting occurs as result of hypermetabolism triggered by ongoing systemic inflammation. In this retrospective study, severely burned patients were analysed for the occurrence of hypernatremia and subsequent signs of hypermetabolism. The urea: creatinine ratio—as a surrogate for hypermetabolism—sufficiently discriminated between two groups. Four of nine hypernatremic burn patients (44%) had a highly elevated urea: creatinine ratio, which was clearly associated with an increased urea production and catabolic index. This hypermetabolism was linked to hypernatremia via an elevated urea- and reduced electrolyte-fraction in renal osmole excretion, which resulted in an increased renal loss of electrolyte-free water. In hypermetabolic severely burned patients, the electrolyte-free water clearance is a major contributor to hypernatremia. A positive correlation to serum sodium concentration was shown.

The Effect of Burn Trauma on Lipid and Glucose Metabolism: Implications for Insulin Sensitivity

Severe burns represent a unique form of trauma in terms of the magnitude and persistence of the stress response they incur. Given advances in acute burn care in the last quarter of a century and the resultant reduction in mortality rates, even for those with massive burns, greater emphasis is now placed on understanding the metabolic stress response to severe burn trauma in order to devise strategies that promote recovery and reduce morbidity. Derangements in metabolism including protein and lipid redistribution and altered glucose handling are hallmarks of the pathophysiological response to burn trauma. In this review article, we aim to distill and discuss the c urrent literature concerning the effect of burn trauma on lipid and glucose metabolism. Furthermore, we will discuss the implications of altered lipid metabolism with regards to insulin sensitivity and glucose control, while discussing the utility of agents and strategies aimed at restoring normal lipid and glucose metabolism in burned patients.

A Critical Update of the Assessment and Acute Management of Patients with Severe Burns

Significance: Burns are debilitating, life threatening, and difficult to assess and manage. Recent advances in assessment and management have occurred since a comprehensive review of the care of patients with severe burns was last published, which may influence research and clinical practice. Recent Advances: Recent advances have occurred in the understanding of burn pathophysiology, which has led to the identification of potential biomarkers of burn severity, such as protein C. There is new evidence about the potential superiority of natural colloids over crystalloids during fluid resuscitation, and new evidence about components of initial and perioperative management, including an improved understanding of pain following burns. Critical Issues: The limitations of the clinical examination highlight the need for imaging and biomarkers to assist in estimations of burn severity. Fluid resuscitation reduces mortality, although there is conjecture over the ideal method. The subsequent perioperative period is associated with significant morbidity and the evidence for preventing and treating pain, infection, and fluid overload while maximizing wound healing potential is described. Future Directions: Promising developments are ongoing in imaging technology, histopathology, biomarkers, and wound healing adjuncts such as hyperbaric oxygen therapy, topical negative pressure therapy, stem cell treatments, and skin substitutes. The greatest benefit from further research on management of patients with burns would most likely be derived from the elucidation of optimal fluid resuscitation protocols, pain management protocols, and surgical techniques from randomized controlled trials.

Energy Expenditure and Protein Requirements Following Burn Injury

Severe burn injuries have long been known to have a profound effect on metabolic equilibrium that can persist after resolution of the cutaneous injuries. Following burn injury, metabolism is a dynamic state resulting in the need for frequent interval reassessment over the course of the care continuum. The acute phase of injury transitions to chronic alterations in macronutrient utilization characterized by futile energy cycling and disproportionate catabolism of skeletal muscle. Protein supplementation appears to be preferentially distributed to the burn wound rather than the skeletal muscle pool. Accurate assessment of caloric and protein requirements is extremely difficult in these patients but is an essential step in efforts to attenuate functional impairment. Indirect calorimetry should be utilized to determine caloric requirements, but trophic feeding strategies are preferred in the initial resuscitative phase to prevent overfeeding while maintaining enteric and immune function. Controversy persists regarding optimal protein targets, and weight-based estimates remain the norm. Exogenous protein and caloric provision performed in isolation is insufficient to optimize outcomes and should be incorporated within a multidisciplinary approach to include muscle loading and pharmaceutical adjuncts.

Burn Trauma Acutely Increases the Respiratory Capacity and Function of Liver Mitochondria

BACKGROUND

A complete understanding of the role of the liver in burn-induced hypermetabolism is lacking. We investigated the acute effect of severe burn trauma on liver mitochondrial respiratory capacity and coupling control as well as the signaling events underlying these alterations.

METHODS

Male BALB/c mice (8-12 weeks) received full-thickness scald burns on ∼30% of the body surface. Liver tissue was harvested 24 h postinjury. Mitochondrial respiration was determined by high-resolution respirometry. Citrate synthase activity was determined as a proxy of mitochondrial density. Male Sprague-Dawley rats received full-thickness scald burns to ∼60% of the body surface. Serum was collected 24 h postinjury. HepG2 cells were cultured with serum-enriched media from either sham- or burn-treated rats. Protein levels were analyzed via western blot.

RESULTS

Mass-specific (P = 0.01) and mitochondrial-specific (P = 0.01) respiration coupled to ATP production significantly increased in the liver after burn. The respiratory control ratio for ADP (P = 0.04) and the mitochondrial flux control ratio (P = 0.03) were elevated in the liver of burned animals. Complex III and Complex IV protein abundance in the liver increased after burn by 17% and 14%, respectively. Exposure of HepG2 cells to serum from burned rats increased the pAMPKα:AMPKα ratio (P < 0.001) and levels of SIRT1 (P = 0.01), Nrf2 (P < 0.001), and PGC1α (P = 0.02).

CONCLUSIONS

Severe burn trauma augments respiratory capacity and function of liver mitochondria, adaptations that augment ATP production. This response may be mediated by systemic factors that activate signaling proteins responsible for regulating cellular energy metabolism and mitochondrial biogenesis.

2,4 Dinitrophenol as Medicine

In the sanctity of pure drug discovery, objective reasoning can become clouded when pursuing ideas that appear unorthodox, but are spot on physiologically. To put this into historical perspective, it was an unorthodox idea in the 1950’s to suggest that warfarin, a rat poison, could be repositioned into a breakthrough drug in humans to protect against strokes as a blood thinner. Yet it was approved in 1954 as Coumadin^® and has been prescribed to billions of patients as a standard of care. Similarly, no one can forget the horrific effects of thalidomide, prescribed or available without a prescription, as both a sleeping pill and “morning sickness” anti-nausea medication targeting pregnant women in the 1950’s. The “thalidomide babies” became the case-in-point for the need of strict guidelines by the U.S. Food & Drug Administration (FDA) or full multi-species teratogenicity testing before drug approval. More recently it was found that thalidomide is useful in graft versus host disease, leprosy and resistant tuberculosis treatment, and as an anti-angiogenesis agent as a breakthrough drug for multiple myeloma (except for pregnant female patients). Decades of diabetes drug discovery research has historically focused on every possible angle, except, the energy-out side of the equation, namely, raising mitochondrial energy expenditure with chemical uncouplers. The idea of “social responsibility” allowed energy-in agents to be explored and the portfolio is robust with medicines of insulin sensitizers, insulin analogues, secretagogues, SGLT2 inhibitors, etc., but not energy-out medicines. The primary reason? It appeared unorthodox, to return to exploring a drug platform used in the 1930s in over 100,000 obese patients used for weight loss. This is over 80-years ago and prior to Dr Peter Mitchell explaining the mechanism of how mitochondrial uncouplers, like 2,4-dinitrophenol (DNP) even worked by three decades later in 1961. Although there is a clear application for metabolic disease, it was not until recently that this platform was explored for its merit at very low, weight-neutral doses, for treating insidious human illnesses and completely unrelated to weight reduction. It is known that mitochondrial uncouplers specifically target the entire organelle’s physiology non-genomically. It has been known for years that many neuromuscular and neurodegenerative diseases are associated with overt production of reactive oxygen species (ROSs), a rise in isoprostanes (biomarker of mitochondrial ROSs in urine or blood) and poor calcium (Ca²⁺) handing. It has also been known that mitochondrial uncouplers lower ROS production and Ca²⁺ overload. There is evidence that elevation of isoprostanes precedes disease onset, in Alzheimer’s Disease (AD). It is also curious, why so many neurodegenerative diseases of known and unknown etiology start at mid-life or later, such as Multiple Sclerosis (MS), Huntington Disease (HD), AD, Parkinson Disease, and Amyotrophic Lateral Sclerosis (ALS). Is there a relationship to a buildup of mutations that are sequestered over time due to ROSs exceeding the rate of repair? If ROS production were managed, could disease onset due to aging be delayed or prevented? Is it possible that most, if not all neurodegenerative diseases are manifested through mitochondrial dysfunction? Although DNP, a historic mitochondrial uncoupler, was used in the 1930s at high doses for obesity in well over 100,000 humans, and so far, it has never been an FDA-approved drug. This review will focus on the application of using DNP, but now, repositioned as a potential disease-modifying drug for a legion of insidious diseases at much lower and paradoxically, weight neutral doses. DNP will be addressed as a treatment for “metabesity”, an emerging term related to the global comorbidities associated with the over-nutritional phenotype; obesity, diabetes, nonalcoholic steatohepatitis (NASH), metabolic syndrome, cardiovascular disease, but including neurodegenerative disorders and accelerated aging. Some unexpected drug findings will be discussed, such as DNP’s induction of neurotrophic growth factors involved in neuronal heath, learning and cognition. For the first time in 80’s years, the FDA has granted (to Mitochon Pharmaceutical, Inc., Blue Bell, PA, USA) an open Investigational New Drug (IND) approval to begin rigorous clinical testing of DNP for safety and tolerability, including for the first ever, pharmacokinetic profiling in humans. Successful completion of Phase I clinical trial will open the door to explore the merits of DNP as a possible treatment of people with many truly unmet medical needs, including those suffering from HD, MS, PD, AD, ALS, Duchenne Muscular Dystrophy (DMD), and Traumatic Brain Injury (TBI).

How long are burn patients really NPO in the perioperative period and can we effectively correct the caloric deficit using an enteral feeding "Catch-up" protocol?

OBJECTIVE

"NPO at midnight" is a standard preoperative practice intended to reduce aspiration risk but can result in prolonged feeding interruptions in critically ill burn patients. Postoperative hyperalimentation in the form of a "catch-up" tube feeding protocol is routine. A retrospective review of our perioperative fasting practices and "catch-up" enteral feeding protocols was performed.

METHODS

Patients admitted to the Burn ICU from July 1st, 2015 to August 31st, 2016 were reviewed. Patients who had a protected airway in place, prescribed enteral nutrition, and underwent surgery were included. The time from NPO to surgical start (NPO-SS), NPO to feeding restart (NPO-FR), and calories received/prescribed were quantified. The efficacy of a postoperative catch-up feeding protocol was analyzed.

RESULTS

There were 41 patients that fit inclusion criteria with some undergoing multiple surgeries, yielding 109 surgeries/discrete perioperative events. The average total body surface area burn (38.1±23.6%), age (38.8±20.1years), ICU days (45.0±37.3 days), and ventilator days (35.1±33.8 days) were calculated. Average fasting durations of NPO-SS and NPO-FR were 9.3±3.1 and 14.2±4.1h, respectively. The average caloric deficit to prescribed calories ratio during the NPO-SS and NPO-FR periods were 1154±629/3534±851kcal and 1765±928/3534±851kcal, respectively. A post-operative catch-up protocol completely compensated for perioperative caloric deficits 68.8% (22/32) of the time.

CONCLUSIONS

In critically ill burn patients, a preoperative fast resulted in an average loss of greater than 50% of prescribed calories on the day of surgery. Clinicians should re-evaluate the standard practice of making preoperative patients "NPO at midnight". An effective catch-up protocol can adequately reduce caloric deficits.

Determinants of skeletal muscle protein turnover following severe burn trauma in children

BACKGROUND & AIMS

Burns remain the fifth cause of non-fatal pediatric injuries globally, with muscle cachexia being a hallmark of the stress response to burns. Burn-induced muscle wasting is associated with morbidity, yet the determinants of muscle protein catabolism in response to burn trauma remains unclear. Our objective was to determine the effect of patient and injury characteristics on muscle protein kinetics in burn patients.

METHODS

This retrospective, observational study was performed using protein kinetic data from pediatric patients who had severe burns (>30% of the total body surface area burned) and underwent cross-limb stable isotope infusions between 1999 and 2008 as part of prospective clinical trials. Mixed multiple regression models were used to assess associations between patient/injury characteristics and muscle protein fractional synthesis rate (FSR), net balance (NB), and rates of phenylalanine appearance (Ra; index of protein breakdown) and disappearance (Rd; index of protein synthesis) across the leg.

RESULTS

A total of 268 patients who underwent 499 studies were analyzed. Increasing time post injury was associated with greater FSR (p < 0.001) and NB (p = 0.01). Males were more catabolic than females (as indicated by lower NB, p = 0.04 and greater Ra, p = 0.008), a consequence of higher protein breakdown rather than lower synthesis. Increasing burn size was associated with higher protein synthesis rate (as indicated by higher FSR, p = 0.019) and higher protein breakdown rates (as indicated by greater Ra, p = 0.001). FSR was negatively associated with age (p < 0.001).

CONCLUSIONS

Data from this large patient cohort show that injury severity, sex, and time post injury influence skeletal muscle wasting in burned children. These findings suggest that individual patient characteristics should be considered when devising therapies to improve the acute care and rehabilitation of burn survivors.

The Role of Serotonin during Skin Healing in Post-Thermal Injury

Post-burn trauma significantly raises tissue serotonin concentration at the initial stages of injury, which leads us to investigate its possible role in post burn wound healing. Therefore, we planned this study to examine the role of serotonin in wound healing through in vitro and in vivo models of burn injuries. Results from in vitro analysis revealed that serotonin decreased apoptosis and increased cell survival significantly in human fibroblasts and neonatal keratinocytes. Cellular proliferation also increased significantly in both cell types. Moreover, serotonin stimulation significantly accelerated the cell migration, resulting in narrowing of the scratch zone in human neonatal keratinocytes and fibroblasts cultures. Whereas, fluoxetine (a selective serotonin reuptake inhibitor) and ketanserin (serotonin receptor 2A inhibitor) reversed these effects. Scald burn mice model (20% total body surface area) showed that endogenous serotonin improved wound healing process in control group, whereas fluoxetine and ketanserin treatments (disruptors of endogenous serotonin stimulation), resulted in poor reepithelization, bigger wound size and high alpha smooth muscle actin (α-SMA) count. All of these signs refer a prolonged differentiation state, which ultimately exhibits poor wound healing outcomes. Collectively, data showed that the endogenous serotonin pathway contributes to regulating the skin wound healing process. Hence, the results of this study signify the importance of serotonin as a potential therapeutic candidate for enhancing skin healing in burn patients.

Metabolic and Endocrine Considerations After Burn Injury

Severe burn injury is followed by a profound hypermetabolic response that persists up to 2 years after injury. It is mediated by up to 50-fold elevations in plasma catecholamines, cortisol, and glucagon that lead to whole-body catabolism, elevated resting energy expenditures, and multiorgan dysfunction. Modulation of the response by early excision and grafting of burn wounds, thermoregulation, control of infection, early and continuous enteral nutrition, and pharmacologic treatments aimed at mitigating physiologic derangements have markedly decreased morbidity.

Nutrition and metabolism in burn patients

Severe burn causes significant metabolic derangements that make nutritional support uniquely important and challenging for burned patients. Burn injury causes a persistent and prolonged hypermetabolic state and increased catabolism that results in increased muscle wasting and cachexia. Metabolic rates of burn patients can surpass twice normal, and failure to fulfill these energy requirements causes impaired wound healing, organ dysfunction, and susceptibility to infection. Adequate assessment and provision of nutritional needs is imperative to care for these patients. There is no consensus regarding the optimal timing, route, amount, and composition of nutritional support for burn patients, but most clinicians advocate for early enteral nutrition with high-carbohydrate formulas.

Nutritional support must be individualized, monitored, and adjusted throughout recovery. Further investigation is needed regarding optimal nutritional support and accurate nutritional endpoints and goals.

Monitoring Energy Metabolism with Indirect Calorimetry: Instruments, Interpretation, and Clinical Application

Indirect calorimetry is the best measure to guide calorie administration during nutrition support. This article presents an update of the types of currently available indirect calorimeters and reviews the recent advances that guide the clinical application of indirect calorimetry. The emphasis of this report is placed on issues that the practicing clinician can use to evaluate, interpret, and apply measurements of energy expenditure.

The Impact of Multimorbidity on Resting Metabolic Rate in Community-Dwelling Women over a Ten-Year Period: A Cross-Sectional and Longitudinal Study

OBJECTIVES

Ageing has been associated with increasing multimorbidity. This study investigated whether the number of diseases is a predictor of resting metabolic rate (RMR) and its long-term changes in community-dwelling elderly women.

SUBJECTS AND DESIGN

Cross-sectional and longitudinal data, obtained over ten years with repeated follow-ups, from 180 women aged 60 - 86 years and with a BMI of 18 - 43 kg/m2 at baseline were analyzed.

MEASUREMENTS

RMR was measured using indirect calorimetry and body composition by bioelectrical impedance analysis. Diagnosed diseases were assessed by a questionnaire comprising 23 disease categories. Subjects with 0 - 2 diseases were classified as relatively healthy and with > 2 diseases as multimorbid.

RESULTS

At baseline, relatively healthy (N = 75) and multimorbid (N = 105) women did not differ in RMR. During the ten-year follow-up, the median (range) number of diseases increased from 2 (0 - 2) to 4 (0 - 8) in relatively healthy and from 5 (3 - 11) to 7 (3 - 15) in multimorbid women. In the longitudinal analyses, only women who were multimorbid at baseline showed a significant increase in RMR of 31 kJ/d per additional disease (P = 0.015), adjusted for fat-free mass, fat mass, waist circumference and age.

CONCLUSION

Increasing multimorbidity in community-dwelling women is associated with an increase in RMR independently of body composition and age.

Nutrition and metabolism in burn patients

Severe burn causes significant metabolic derangements that make nutritional support uniquely important and challenging for burned patients. Burn injury causes a persistent and prolonged hypermetabolic state and increased catabolism that results in increased muscle wasting and cachexia. Metabolic rates of burn patients can surpass twice normal, and failure to fulfill these energy requirements causes impaired wound healing, organ dysfunction, and susceptibility to infection. Adequate assessment and provision of nutritional needs is imperative to care for these patients. There is no consensus regarding the optimal timing, route, amount, and composition of nutritional support for burn patients, but most clinicians advocate for early enteral nutrition with high-carbohydrate formulas. Nutritional support must be individualized, monitored, and adjusted throughout recovery. Further investigation is needed regarding optimal nutritional support and accurate nutritional endpoints and goals.

Long-Term Skeletal Muscle Mitochondrial Dysfunction is Associated with Hypermetabolism in Severely Burned Children

The long-term impact of burn trauma on skeletal muscle bioenergetics remains unknown. Here, the authors determined respiratory capacity and function of skeletal muscle mitochondria in healthy individuals and in burn victims for up to 2 years postinjury. Biopsies were collected from the m. vastus lateralis of 16 healthy men (26 ± 4 years) and 69 children (8 ± 5 years) with burns encompassing ≥30% of their total BSA. Seventy-nine biopsies were collected from cohorts of burn victims at 2 weeks (n = 18), 6 months (n = 18), 12 months (n = 25), and 24 months (n = 18) postburn. Hypermetabolism was determined by the difference in predicted and measured metabolic rate. Mitochondrial respiration was determined in saponin-permeabilized myofiber bundles. Outcomes were modeled by analysis of variance, with differences in groups assessed by Tukey-adjusted contrasts. Burn patients were hypermetabolic for up to 2 years postinjury. Coupled mitochondrial respiration was lower at 2 weeks (17 [8] pmol/sec/mg; P < .001), 6 months (41 [30] pmol/sec/mg; P = .03), and 12 months (35 [14] pmol/sec/mg; P < .001) postburn compared with healthy controls (58 [13] pmol/sec/mg). Coupled respiration was greater at 6, 12, and 24 months postburn vs 2 weeks postburn (P < .001). Mitochondrial adenosine diphosphate and oligomycin sensitivity (measures of coupling control) were lower at all time-points postburn vs control (P < .05), but greater at 6, 12, and 24 months postburn vs 2 weeks postburn (P < .05). Muscle mitochondrial respiratory capacity remains significantly lower in burn victims for 1-year postinjury. Mitochondrial coupling control is diminished for up to 2 years postinjury in burn victims, resulting in greater mitochondrial thermogenesis. These quantitative and qualitative derangements in skeletal muscle bioenergetics likely contribute to the long-term pathophysiological stress response to burn trauma.

The impact of non-severe burn injury on cardiac function and long-term cardiovascular pathology

Severe burn injury significantly affects cardiovascular function for up to 3 years. However, whether this leads to long-term pathology is unknown. The impact of non-severe burn injury, which accounts for over 80% of admissions in developed countries, has not been investigated. Using a rodent model of non-severe burn injury with subsequent echocardiography we showed significantly increased left ventricular end systolic diameter (LVESD) and ventricular wall thickness at up to 3 months post-injury. Use of propranolol abrogated the changes in cardiac measures observed. Subsequently we investigated changes in a patient cohort with non-severe injury. Echocardiography measured at baseline and at 3 months post-injury showed increased LVESD at 3 months and significantly decreased posterior wall diameter. Finally, 32 years of Western Australian hospital records were used to investigate the incidence of cardiovascular disease admissions after burn injury. People who had experienced a burn had increased hospital admissions and length of stay for cardiovascular diseases when compared to a matched uninjured cohort. This study presents animal, patient and population data that strongly suggest non-severe burn injury has significant effects on cardiovascular function and long-term morbidity in some burn patients. Identification of patients at risk will promote better intervention and outcomes for burn patients.

The metabolic stress response to burn trauma: current understanding and therapies

Major burns provoke a profound stress response, which is unrivalled in terms of its magnitude and duration. Evidence suggests that the pathophysiological stress response to severe burn trauma persists for several years after injury. Thus, there is a pressing need for novel strategies that mitigate this response and restore normal metabolic function in patients with burns. This is the first in a Series of three papers about the care of people with burns. In this paper, we review the current knowledge of the stress response to burn trauma, with a focus on hypermetabolism, muscle wasting, and stress-induced diabetes. We highlight recent developments and important knowledge gaps that need to be pursued to develop novel therapeutic strategies to improve outcomes in burn survivors.

Kidney and Liver Injuries After Major Burns in Rats Are Prevented by Resolvin D2

OBJECTIVES

Innate immune dysfunction after major burn injuries increases the susceptibility to organ failure. Lipid mediators of inflammation resolution, e.g., resolvin D2, have been shown recently to restore neutrophil functionality and reduce mortality rate in a rat model of major burn injury. However, the physiological mechanisms responsible for the benefic activity of resolvin D2 are not well understood.

DESIGN

Prospective randomized animal investigation.

SETTING

Academic research setting.

SUBJECTS

Wistar male rats.

INTERVENTIONS

Animals were subjected to a full-thickness burn of 30% total body surface area. Two hours after burn, 25 ng/kg resolvin D2 was administered IV and repeated every day, for 8 days. At day 10 post burn, 2 mg/kg of lipopolysaccharide was administered IV, and the presence of renal and hepatic injuries was evaluated at day 11 post burn by histology, immunohistochemistry, and relevant blood chemistry.

MEASUREMENTS AND MAIN RESULTS

In untreated animals, we found significant tissue damage in the kidneys and liver, consistent with acute tubular necrosis and multifocal necrosis, and changes in blood chemistry, reflecting the deterioration of renal and hepatic functions. We detected less tissue damage and significantly lower values of blood urea nitrogen (26.4 ± 2.1 vs 36.0 ± 9.3 mg/dL; p ≤ 0.001), alanine aminotransferase (266.5 ± 295.2 vs 861.8 ± 813.7 U/L; p ≤ 0.01), and total bilirubin (0.13 ± 0.05 vs 0.30 ± 0.14 mg/dL; p ≤ 0.01) in resolvin D2-treated rats than in untreated animals. The mean blood pressure of all animals was above 65 mm Hg, indicating adequate tissue perfusion throughout the experiments. We measured significantly larger amounts of chromatin in the circulation of untreated than of resolvin D2-treated rats (575.1 ± 331.0 vs 264.1 ± 122.4 ng/mL; p ≤ 0.05) and identified neutrophil extracellular traps in kidney and liver tissues from untreated rats, consistent with the tissue damage.

CONCLUSIONS

Pathologic changes in kidney and liver tissues in a rat model of major burn and endotoxin insults are ameliorated by resolvin D2.

Severe Burn Injury Induces Thermogenically Functional Mitochondria in Murine White Adipose Tissue

Chronic cold exposure induces functionally thermogenic mitochondria in the inguinal white adipose tissue (iWAT) of mice. Whether this response occurs in pathophysiological states remains unclear. The purpose of this study was to determine the impact of severe burn trauma on iWAT mitochondrial function in mice. Male BALB/c mice (10-12 weeks) received full-thickness scald burns to ∼30% of the body surface area. Inguinal white adipose tissue was harvested from mice at 1, 4, 10, 20, and 40 days postinjury. Total and uncoupling protein 1 (UCP1)-dependent mitochondrial thermogenesis were determined in iWAT. Citrate synthase activity was determined as a proxy of mitochondrial abundance. Immunohistochemistry was performed to assess iWAT morphology and UCP1 expression. Uncoupling protein 1-dependent respiration was significantly greater at 4 and 10 days after burn compared with sham, peaking at 20 days after burn (P < 0.001). Citrate synthase activity was threefold greater at 4, 10, 20, and 40 days after burn versus sham (P < 0.05). Per mitochondrion, UCP1 function increased after burn trauma (P < 0.05). After burn trauma, iWAT exhibited numerous multilocular lipid droplets that stained positive for UCP1. The current findings demonstrate the induction of thermogenically competent mitochondria within rodent iWAT in a model of severe burn trauma. These data identify a specific pathology that induces the browning of white adipose tissue in vivo and may offer a mechanistic explanation for the chronic hypermetabolism observed in burn victims.

WITHDRAWN: Early enteral nutrition versus late enteral nutrition for burns patients: A systematic review and meta-analysis

This article has been withdrawn at the request of the authors. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Differential acute and chronic effects of burn trauma on murine skeletal muscle bioenergetics

Altered skeletal muscle mitochondrial function contributes to the pathophysiological stress response to burns. However, the acute and chronic impact of burn trauma on skeletal muscle bioenergetics remains poorly understood. Here, we determined the temporal relationship between burn trauma and mitochondrial function in murine skeletal muscle local to and distal from burn wounds. Male BALB/c mice (8-10 weeks old) were burned by submersion of the dorsum in water (∼ 95 °C) to create a full thickness burn on ∼ 30% of the body. Skeletal muscle was harvested spinotrapezius underneath burn wounds (local) and the quadriceps (distal) of sham and burn treated mice at 3h, 24h, 4d and 10d post-injury. Mitochondrial respiration was determined in permeabilized myofiber bundles by high-resolution respirometry. Caspase 9 and caspase 3 protein concentration were determined by western blot. In muscle local to burn wounds, respiration coupled to ATP production was significantly diminished at 3h and 24h post-injury (P<0.001), as was mitochondrial coupling control (P<0.001). There was a 5- (P<0.05) and 8-fold (P<0.001) increase in respiration in response to cytochrome at 3h and 24h post burn, respectively, indicating damage to the outer mitochondrial membranes. Moreover, we also observed greater active caspase 9 and caspase 3 in muscle local to burn wounds, indicating the induction of apoptosis. Distal muscle mitochondrial function was unaltered by burn trauma until 10d post burn, where both respiratory capacity (P<0.05) and coupling control (P<0.05) were significantly lower than sham. These data highlight a differential response in muscle mitochondrial function to burn trauma, where the timing, degree and mode of dysfunction are dependent on whether the muscle is local or distal to the burn wound.

Skeletal Muscle Protein Breakdown Remains Elevated in Pediatric Burn Survivors up to One-Year Post-Injury

Acute alterations in skeletal muscle protein metabolism are a well-established event associated with the stress response to burns. Nevertheless, the long-lasting effects of burn injury on skeletal muscle protein turnover are incompletely understood. This study was undertaken to investigate fractional synthesis (FSR) and breakdown (FBR) rates of protein in skeletal muscle of pediatric burn patients (n  =  42, >30% total body surface area burns) for up to 1 year after injury. Skeletal muscle protein kinetics were measured in the post-prandial state following bolus injections of C6 and N phenylalanine stable isotopes. Plasma and muscle phenylalanine enrichments were quantified using gas chromatography-mass spectrometry. We found that the FSR in burn patients was 2- to 3-fold higher than values from healthy men previously reported in the literature (P ≤ 0.05). The FBR was 4- to 6-fold higher than healthy values (P  <  0.01). Therefore, net protein balance was lower in burn patients compared with healthy men from 2 weeks to 12 months post-injury (P  <  0.05). These findings show that skeletal muscle protein turnover stays elevated for up to 1 year after burn, an effect attributable to simultaneous increases in FBR and FSR. Muscle FBR exceeds FSR during this time, producing a persistent negative net protein balance, even in the post-prandial state, which likely contributes to the prolonged cachexia seen in burned victims.

Nutrition and anabolic pharmacotherapies in the care of burn patients

Thermal injury is a devastating injury that results in a number of pathological alterations in almost every system in the body. Hypermetabolism, muscle wasting, depressed immunity, and impaired wound healing are all clinical features of burns. Failure to address each of these specific pathological alterations can lead to increased mortality. Nutrition supplementation has been recommended as a therapeutic tool to help attenuate the hypermetabolism and devastating catabolism evident following burn. Despite the wide consensus on the need of nutrition supplementation in burn patients, controversy exists with regard to the type and amount of nutrition recommended. Nutrition alone is also not enough in these patients to halt and reverse some of the damage done by the catabolic pathways activated following severe burn injury. This has led to the use of anabolic pharmacologic agents in conjunction with nutrition to help improve patient outcome following burn injury. In this review, we examine the relevant literature on nutrition after burn injury and its contribution to the attenuation of the postburn hypermetabolic response, impaired wound healing, and suppressed immunological responses. We also review the commonly used anabolic agents clinically in the care of burn patients. Finally, we provide nutrition and pharmacological recommendations gained from prospective trials, retrospective analyses, and expert opinions based on our practice at the Ross Tilley Burn Center in Toronto, Canada.

Browning of Subcutaneous White Adipose Tissue in Humans after Severe Adrenergic Stress

Since the presence of brown adipose tissue (BAT) was confirmed in adult humans, BAT has become a therapeutic target for obesity and insulin resistance. We examined whether human subcutaneous white adipose tissue (sWAT) can adopt a BAT-like phenotype using a clinical model of prolonged and severe adrenergic stress. sWAT samples were collected from severely burned and healthy individuals. A subset of burn victims were prospectively followed during their acute hospitalization. Browning of sWAT was determined by the presence of multilocular adipocytes, uncoupling protein 1 (UCP1), and increased mitochondrial density and respiratory capacity. Multilocular UCP1-positive adipocytes were found in sWAT samples from burn patients. UCP1 mRNA, mitochondrial density, and leak respiratory capacity in sWAT increased after burn trauma. Our data demonstrate that human sWAT can transform from an energy-storing to an energy-dissipating tissue, which opens new research avenues in our quest to prevent and treat obesity and its metabolic complications.

Do β-Blockers Decrease the Hypermetabolic State in Critically Ill Children With Severe Burns?

BACKGROUND AND OBJECTIVES

Severe burns result in a hypermetabolic state that is associated with increased morbidity and mortality. We reviewed the literature to determine if there is strong evidence that short-term β-blockers reduce the hypermetabolic state or mortality and length of stay (LOS) compared with no therapy in patients with severe burns.

METHODS

A literature search of PubMed, Embase, the Cochrane Database of Systematic Reviews, and BestBETs was conducted on the use of adrenergic β-antagonists in burn patients.

RESULTS

Six randomized controlled trials met the inclusion criteria. Five pediatric trials found that β-blockers reduced the hypermetabolic state (as defined by reduction of cardiac work, rate pressure product, resting energy expenditure, central deposition of fat, and bone mineral loss) and were associated with an improvement in lean muscle mass in patients with severe burns. However, there was no change in LOS or mortality in these children. One adult study in burn patients found shorter LOS in patients treated with β-blockers but no difference in mortality rate. β-blockers were relatively well tolerated, with no differences in adverse effects reported.

CONCLUSIONS

β-blockers seem to reduce the hypermetabolic state in pediatric patients with burns, but there is insufficient evidence to suggest they have an impact on mortality rates or LOS.

The role of exercise in the rehabilitation of patients with severe burns

Severe burn trauma results in persistent skeletal muscle catabolism and prolonged immobilization. We hypothesize that structured rehabilitative exercise is a safe and efficacious strategy to restore lean body mass and physical function in burn victims. Here, we review the evidence for the utility of rehabilitative exercise training in restoring physiological function in burn survivors.

Nutrition and metabolism in the rehabilitative phase of recovery in burn children: a review of clinical and research findings in a speciality pediatric burn hospital

During the rehabilitation phase of burn injury, patient care transitions from critical care medicine to restorative treatment strategies that encompass physical and occupational therapies, nutrition repletion, and psychosocial support for community reintegration. As pediatric burn patients undergo rehabilitation, nutrition assessment remains ongoing to define nutritional status and any alterations in metabolism that may take place. For some, a persistent hypermetabolic state appears evident, and weight loss may continue. The severity and duration however varies among patients. Many patients enter their rehabilitative phase with visible lean body mass depletion, and the focus of nutritional therapy for them shifts to replenishing nutritional status, while supporting rehabilitative efforts. Over the past decade, we have conducted studies on energy and protein metabolism, body composition, including bone mineralization, and general wellness in over 130 patients to better understand changes in metabolism and nutritional status during the rehabilitative phase of recovery. This abstract summarizes our findings.

Resting Energy Expenditure in Patients with Stroke during the Subacute Phases - Relationships with Stroke Types, Location, Severity of Paresis, and Activities of Daily Living

BACKGROUND

The energy demands in patients with stroke during the subacute phases are unclear. However, this information is essential for appropriate clinical and nutritional management. The aims of this study were to determine the resting energy expenditure (REE) during the subacute phases, examine its relationships with stroke types, location, severity of hemiparesis, and activities of daily living (ADL), and evaluate whether estimation of REE from the Harris-Benedict equation (HB) requires the addition of a 'stress factor' to capture possible additional REE imposed by stroke.

METHODS

We measured REE in 95 patients with subacute stroke (53.5 ± 16.6 days post-stroke) with indirect calorimetry, and compared it with predicted values of energy expenditure estimated from the HB (expressed as percentage). Patients were admitted for rehabilitation of their first ischemic or nonsurgical hemorrhagic stroke. The severity of hemiparesis was assessed with the motor items of the Stroke Impairment Assessment Set (SIAS). The ADL was assessed with the Functional Independence Measure (FIM). We compared REE and %HB of the two groups divided by hemiparesis severity and ADL limitation using the Student's t-test, and those of the five groups divided by stroke location. The correlations between REE and the motor items of the SIAS and the FIM score were assessed with the Spearman rank correlation test. A multiple regression analysis for REE was conducted.

RESULTS

The average body weight (BW) was 57.1 ± 11.3 kg. The average body mass index (BMI) was 22.5 ± 4.0. The mean REE (%HB) was 1,271 ± 284 kcal/day (106.0 ± 17.3%). REE and %HB of the low ADL group was less than that of the high ADL group (p < 0.05). The REE had a positive correlation with the FIM score (rs = 0.51, p < 0.01). The motor items of the SIAS were not significantly correlated with REE. BW, FIM, and stroke location were independent predictors of REE.

CONCLUSIONS

Analysis of energy expenditure suggests that stroke patients are not hypermetabolic during the subacute phase. The 'stress factor' in stroke patients during the subacute phase was 1.0-1.1. This finding provides important information for improving nutritional management during the subacute phase in patients with stroke.

The Therapeutic Potential of Brown Adipocytes in Humans

Obesity and its metabolic consequences represent a significant clinical problem. From a thermodynamic standpoint, obesity results from a discord in energy intake and expenditure. To date, lifestyle interventions based on reducing energy intake and/or increasing energy expenditure have proved ineffective in the prevention and/or treatment of obesity, owing to poor long-term adherence to such interventions. Thus, an effective strategy to prevent or correct obesity is currently lacking. As the combustion engines of our cells, mitochondria play a critical role in energy expenditure. At a whole-body level, approximately 80% of mitochondrial membrane potential generated by fuel oxidation is used to produce ATP, and the remaining 20% is lost through heat-producing uncoupling reactions. The coupling of mitochondrial respiration to ATP production represents an important component in whole-body energy expenditure. Brown adipose tissue (BAT) is densely populated with mitochondria containing the inner mitochondrial proton carrier uncoupling protein 1 (UCP1). UCP1 uncouples oxidative phosphorylation, meaning that mitochondrial membrane potential is dissipated as heat. The recent rediscovery of BAT depots in adult humans has rekindled scientific interest in the manipulation of mitochondrial uncoupling reactions as a means to increase metabolic rate, thereby counteracting obesity and its associated metabolic phenotype. In this article, we discuss the evidence for the role BAT plays in metabolic rate and glucose and lipid metabolism in humans and the potential for UCP1 recruitment in the white adipose tissue of humans. While the future holds much promise for a therapeutic role of UCP1 expressing adipocytes in human energy metabolism, particularly in the context of obesity, tissue-specific strategies that activate or recruit UCP1 in human adipocytes represent an obligatory translational step for this early promise to be realized.

The regenerative potential of epithelial stem cells in tissue repair

Acute and chronic wounds encompass devastating injuries with significant physical, emotional and economic costs at both the individual and societal level. The pathogenesis of chronic wounds is as varied as the potential causes; however, contributing factors include repetitive ischaemia/reperfusion injury coupled with bacterial infection, inflammation and matrix degradation at the wound site. Similarly, the acute physical damage of burns may leave patients vulnerable to dehydration and infection, and in certain cases this may be followed by a body-wide systemic response with debilitating consequences. Epithelial stem cells provide a promising avenue for the treatment of burns and chronic wounds. This is exemplified by recent achievements such as the restoration of corneal epithelium using limbal stem cells, and the treatment of epidermolysis bullosa via a gene therapy approach. Nevertheless, many technical and regulatory challenges remain to be addressed. This article is part of a Directed Issue entitled: Regenerative Medicine: the challenge of translation.

Changes in fat distribution in children following severe burn injury

BACKGROUND

Children with severe cutaneous burn injury show persistent metabolic abnormalities, including inflammation and insulin resistance. Such abnormalities could potentially increase their future risk for developing type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). This could be related to changes in body composition and fat distribution.

METHODS

We studied body composition, fat distribution, and inflammatory cytokines changes in children with severe burn injury up to 6 months from discharge. Sixty-two boys and 35 girls (burn ≥30% of total body surface area) were included.

RESULTS

We found a decrease in total body fat and subcutaneous peripheral fat at 6 months (6% and 2%, respectively; P<0.05 each). An inverse correlation between the decrease in peripheral fat content at 6 months and the extent of burn injury (r=-041, P=0.02) was also observed. In addition, there was a 12% increase in serum tumor necrosis factor-α (TNF-α) (P=0.01 vs. discharge) and 9% decrease in serum interleukin-10 (IL-10) (P<0.0001 vs. discharge) over 6 months after burn.

CONCLUSION

Severe burn injury in children is associated with changes in body fat content and distribution up to 6 months from hospital discharge. These changes, accompanied by persisting systemic inflammation, could possibly mediate the observed persistence of insulin resistance, predisposing burn patients to the development of T2DM and CVD.