Temporal changes in cellular energy following burn injury

The Effect of Betulin Diphosphate in Wound Dressings of Bacterial Cellulose-ZnO NPs on Platelet Aggregation and the Activity of Oxidoreductases Regulated by NAD(P)+/NAD(P)H-Balance in Burns on Rats

The inhibition of platelet aggregation, and the activity of oxidoreductases and microhemocirculation in a burn wound on the treatment of burns with wound dressings based on bacterial nanocellulose (BC)-zinc oxide nanoparticles (ZnO NPs)-betulin diphosphate (BDP) were studied. The control of the treatment by BC-ZnO NPs-BDP on burned rats by the noninvasive DLF method showed an increase in perfusion and the respiratory component in wavelet spectra, characterizing an improvement in oxygen saturation in the wound. The study on the volunteers' blood found the inhibition of ADP-induced platelet aggregation by 30-90%. Disaggregation depends on the dose under the action of the ionized form of BDP and ZnO NPs-BDP in a phosphate buffer; it was reversible and had two waves. It was shown on rats that the specific activity of LDHreverse and LDHdirect (control-intact animals) on day 21 of treatment increased by 11-38% and 23%, respectively. The LDHreverse/LDHdirect ratio increased at BC-ZnO NPs-BDP treatment, which characterizes efficient NAD+ regeneration. AlDH activity increased significantly in the first 10 days by 70-170%, reflecting the effectiveness of the enzyme and NAD+ in utilizing toxic aldehydes at this stage of burn disease. The activities of GR and G6PDH using NADP(H) were increased with BC-ZnO NPs-BDP treatment.

Metformin alleviates muscle wasting post-thermal injury by increasing Pax7-positive muscle progenitor cells

BACKGROUND

Profound skeletal muscle wasting and weakness is common after severe burn and persists for years after injury contributing to morbidity and mortality of burn patients. Currently, no ideal treatment exists to inhibit muscle catabolism. Metformin is an anti-diabetic agent that manages hyperglycemia but has also been shown to have a beneficial effect on stem cells after injury. We hypothesize that metformin administration will increase protein synthesis in the skeletal muscle by increasing the proliferation of muscle progenitor cells, thus mitigating muscle atrophy post-burn injury.

METHODS

To determine whether metformin can attenuate muscle catabolism following burn injury, we utilized a 30% total burn surface area (TBSA) full-thickness scald burn in mice and compared burn injuries with and without metformin treatment. We examined the gastrocnemius muscle at 7 and 14 days post-burn injury.

RESULTS

At 7 days, burn injury significantly reduced myofiber cross-sectional area (CSA) compared to sham, p < 0.05. Metformin treatment significantly attenuated muscle catabolism and preserved muscle CSA at the sham size. To investigate metformin's effect on satellite cells (muscle progenitors), we examined changes in Pax7, a transcription factor regulating the proliferation of muscle progenitors. Burned animals treated with metformin had a significant increase in Pax7 protein level and the number of Pax7-positive cells at 7 days post-burn, p < 0.05. Moreover, through BrdU proliferation assay, we show that metformin treatment increased the proliferation of satellite cells at 7 days post-burn injury, p < 0.05.

CONCLUSION

In summary, metformin's various metabolic effects and its modulation of stem cells make it an attractive alternative to mitigate burn-induced muscle wasting while also managing hyperglycemia.

Hepatic autophagy after severe burn in response to endoplasmic reticulum stress

BACKGROUND

Previous studies showed that liver dysfunction develops soon after severe burn, and this is associated with activation of endoplasmic reticulum (ER) stress. Autophagy is a catabolic process to maintain cellular organelle balance; ER stress is associated with autophagy signaling cascades. We thus sought to determine whether autophagy signals were associated with damage in the liver after burn, and further whether burn-associated ER stress activates autophagy signals in hepatocytes.

METHODS

C57BL/6 male mice received a 25% total body surface area full-thickness scald burn, and liver was harvested at 24 h after burn. HepG2 cells were stimulated with an ER stress inducer thapsigargin (TG) for 24 h to mimic ER stress in vitro. Terminal deoxyuridine nick-end labeling staining was performed on histologic sections of liver. Autophagy was assessed by immunoblotting. Statistical analysis was performed using the Student t-test and significance was accepted at P < 0.05.

RESULTS

Terminal deoxyuridine nick-end labeling positive-stained hepatocytes increased in burned animals with a significant elevation of caspase 3 activity (P < 0.05). Hepatic autophagy-related (ATG) protein 3, ATG5 and light chain (LC) 3B elevated significantly in burn animals as well (P < 0.05). Expression of Beclin-1, LC3A, and LC3B increased in HepG2 cells in response to TG, similar to the response seen in vivo. Cytosolic adenosine triphosphate dropped significantly, and adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) were phosphorylated as well in response to TG (P < 0.05).

CONCLUSIONS

ER stress, which occurs in hepatocytes after severe injury, is associated with autophagy and liver damage after severe burn. In response to ER stress, activated autophagy is associated with adenosine monophosphate-activated protein kinase and mammalian target target of rapamycin pathway.

Development of Metabolic Indicators of Burn Injury: Very Low Density Lipoprotein (VLDL) and Acetoacetate Are Highly Correlated to Severity of Burn Injury in Rats

Hypermetabolism is a significant sequela to severe trauma such as burns, as well as critical illnesses such as cancer. It persists in parallel to, or beyond, the original pathology for many months as an often-fatal comorbidity. Currently, diagnosis is based solely on clinical observations of increased energy expenditure, severe muscle wasting and progressive organ dysfunction. In order to identify the minimum number of necessary variables, and to develop a rat model of burn injury-induced hypermetabolism, we utilized data mining approaches to identify the metabolic variables that strongly correlate to the severity of injury. A clustering-based algorithm was introduced into a regression model of the extent of burn injury. As a result, a neural network model which employs VLDL and acetoacetate levels was demonstrated to predict the extent of burn injury with 88% accuracy in the rat model. The physiological importance of the identified variables in the context of hypermetabolism, and necessary steps in extension of this preliminary model to a clinically utilizable index of severity of burn injury are outlined.

Mouse closed head injury model induced by a weight-drop device

Traumatic brain injury represents the leading cause of death in young individuals. Various animal models have been developed to mimic human closed head injury (CHI). Widely used models induce head injury by lateral fluid percussion, a controlled cortical impact or impact acceleration. The presented model induces a CHI by a standardized weight-drop device inducing a focal blunt injury over an intact skull without pre-injury manipulations. The resulting impact triggers a profound neuroinflammatory response within the intrathecal compartment with high consistency and reproducibility, leading to neurological impairment and breakdown of the blood-brain barrier. In this protocol, we define standardized procedures for inducing CHI in mice and determine various severity grades of CHI through modulation of the weight falling height. In experienced hands, this CHI model can be carried out in as little as 30 s per animal, with additional time required for subsequent posttraumatic analysis and data collection.

Aging and animal models of systemic insult: trauma, burn, and sepsis

In the acute-care setting, it is widely accepted that elderly patients have increased morbidity and mortality compared with young healthy patients. The reasons for this, however, are largely unknown. Although animal modeling has helped improve treatment strategies for young patients, there are a scarce number of studies attempting to understand the mechanisms of systemic insults such as trauma, burn, and sepsis in aged individuals. This review aims to highlight the relevance of using animals to study the pathogenesis of these insults in the aged and, despite the deficiency of information, to summarize what is currently known in this field.

Insulin sensitivity is related to fat oxidation and protein kinase C activity in children with acute burn injury

Impaired fatty acid oxidation occurs with type 2 diabetes and is associated with accumulations of intracellular lipids, which may increase diacylglycerol (DAG), stimulate protein kinase C activity, and inactivate insulin signaling. Glucose and fat metabolism are altered in burn patients, but have never been related to intracellular lipids or insulin signaling. Thirty children sustaining >40% total body surface area burns were studied acutely with glucose and palmitate tracer infusions and a hyper-insulinemic euglycemic clamp. Muscle triglyceride, DAG, fatty acyl CoA, and insulin signaling were measured. Liver and muscle triglyceride levels were measured with magnetic resonance spectroscopy. Muscle samples from healthy children were controls for DAG concentrations. Insulin sensitivity was reduced and correlated with whole body palmitate beta-oxidation (P = .004). Muscle insulin signaling was not stimulated by hyper-insulinemia. Tissue triglyceride concentrations and activated protein kinase C-beta were elevated, whereas the concentration of DAG was similar to the controls. Free fatty acid profiles of muscle triglyceride did not match DAG. Insulin resistance following burn injury is accompanied by decreased insulin signaling and increased protein kinase C-beta activation. The best metabolic predictor of insulin resistance in burned patients was palmitate oxidation.

Human mitochondrial oxidative capacity is acutely impaired after burn trauma

BACKGROUND

Mitochondrial proteins and genes are damaged after burn injury in animals and are assessed in human burn patients in this study.

METHODS

The rates of maximal muscle mitochondrial oxidative capacity (adenosine triphosphate production) and uncoupled oxidation (heat production) for both palmitate and pyruvate were measured in muscle biopsies from 40 children sustaining burns on more than 40% of their body surface area and from 13 healthy children controls.

RESULTS

Maximal mitochondrial oxidation of pyruvate and palmitate were reduced in burn patients compared with controls (4.0 +/- .2:1.9 +/- .1 micromol O2/citrate synthase activity/mg protein/min pyruvate; control:burn; P < .001 and 3.0 +/- .1: .9 +/- .03 micromol O2/citrate synthase activity/mg protein/min palmityl CoA; control:burn; P = .003). Uncoupled oxidation was the same between groups.

CONCLUSIONS

The maximal coupled mitochondrial oxidative capacity is severely impaired after burn injury, although there are no alterations in the rate of uncoupled oxidative capacity. It may be that the ratio of these indicates that a larger portion of energy production in trauma patients is wasted through uncoupling, rather than used for healing.

Recovery of labeled CO2 from acetate in severely burned children

The purpose of this study was to determine the fractional recovery rate of labeled CO(2) in the breath of severely burned children. This information is needed to perform tracer studies of substrate oxidation using carbon-labeled fatty acids. Nine children, ages 4-14 yr with massive burns participated in the study. All experiments were performed 7 days post burn after an overnight fast. A primed (60 micromol/kg), constant (2.0 micromol.kg(-1).min(-1)) infusion of [1,2-(13)C]acetate was given during a 4-h basal period and during a 4-h hyperinsulinemic euglycemic clamp. A priming dose (150 micromol/kg) of NaH(13)CO(3) was given at the beginning of the study. Breath samples were collected every 10 min during the last 40 min of each period. Indirect calorimetry was performed during the last 30 min of each period. The isotopic enrichment of (13)CO(2) was determined by isotope ratio-mass spectrometry, and total CO(2) excretion was measured by indirect calorimetry. The fractional recovery of acetate label was 0.89 +/- 0.05 and 0.88 +/- 0.04 during the basal state and clamp, respectively. We conclude that the fractional recovery of labeled acetate in severely burned children is approximately three times the recovery of a nonburned adult and similar to the value in exercising adults. The high recovery rate reflects the rapid turnover of the TCA cycle in burned children relative to the rate of exchange reactions. Minimal correction of expired CO(2) data is needed in this circumstance to quantify fatty acid oxidation using (13)C-labeled fatty acids.