Effects of metformin on burn-induced hepatic endoplasmic reticulum stress in male rats

Evaluation and HPLC characterisation of a new herbal ointment for the treatment of full-thickness burns in rats

Objective

Burn injuries are among the most common accidental health problems worldwide, frequently leading to health and socio-economic challenges. Despite this, no standard protocol for managing burn injuries can overcome the adverse effects of currently used drugs. The present study sets out to develop and evaluate the efficacy of new herbal ointments in providing synergistic anti-inflammatory, antimicrobial, antioxidant, and cell-proliferating activities. It also investigates the high-performance liquid chromatography (HPLC) characterisation of these new herbal ointments.

Method

Three different concentrations of the new herbal ointment, which incorporates extracts of Matricaria aurea flower heads, arial parts of Calendula tripterocarpa, Rosmarinus officinalis leaves, Alkanna tinctoria roots, and myrrh were developed and evaluated. Ointments designed to promote burn-wound healing were prepared and compared with β-sitosterol ointment and silver sulfadiazine cream, as a commercial standards.

Results

According to statistical and histopathological analyses and visual inspections, the new herbal formulas showed faster wound healing, more tolerability, and less toxicity than the commercial standards.

Conclusion

The new herbal ointments, developed in our study, have shown promising results. The formula offers mechanical protection without any release of non-biodegradable particles. It maintains the optimum moisture and pH of the skin, while minimising scar-tissue formation. These advantages, in addition to availability, low costs, and easy handling, may support the use of this new herbal formula as an effective and safe alternative treatment, designed to promote the healing of burn injuries.

Third-degree burn mouse treatment using recombinant human fibroblast growth factor 2

Fibroblast growth factor 2 (FGF-2) is a multifunctional protein that has major roles in wound healing, tissue repair, and regeneration. This therapeutic protein is widely used for burn treatment because it can stimulate cell proliferation and differentiation, angiogenesis, and extracellular matrix remodeling. In this study, we developed a simple method using a controlled heated brass rod to create a homogenous third-degree burn murine model and evaluated the treatment using recombinant human FGF-2 (rhFGF-2). The results indicated that the wound area was 0.83 ± 0.05 cm² and wound depth was 573.42 ± 147.82 μm. Mice treated with rhFGF-2 showed higher rates of wound closure, granulation tissue formation, angiogenesis, and re-epithelialization than that of phosphate-buffered saline (PBS)-treated group. In conclusion, our lab-made rhFGF-2 could be a potentially therapeutic protein for burn treatment as well as a bioequivalent drug for other commercial applications using FGF-2.

Alcohol Modulation of the Postburn Hepatic Response

The widespread and rapidly increasing trend of binge drinking is accompanied by a concomitant rise in the prevalence of trauma patients under the influence of alcohol at the time of their injury. Epidemiological evidence suggests up to half of all adult burn patients are intoxicated at the time of admission, and the presence of alcohol is an independent risk factor for death in the early stages post burn. As the major site of alcohol metabolism and toxicity, the liver is a critical determinant of postburn outcome, and experimental evidence implies an injury threshold exists beyond which burn-induced hepatic derangement is observed. Alcohol may lower this threshold for postburn hepatic damage through a variety of mechanisms including modulation of extrahepatic events, alteration of the gut-liver axis, and changes in signaling pathways. The direct and indirect effects of alcohol may prime the liver for the second-hit of many overlapping physiologic responses to burn injury. In an effort to gain a deeper understanding of how alcohol potentiates postburn hepatic damage, the authors summarize possible mechanisms by which alcohol modulates the postburn hepatic response.

Role of intestinal trefoil factor in protecting intestinal epithelial cells from burn-induced injury

Although intestinal trefoil factor (ITF) can alleviate the burn-induced intestinal mucosa injury, the underlying mechanisms remains elusive. In this study, we investigated if ITF alters glutamine transport on the brush border membrane vesicles (BBMVs) of the intestines in Sprague-Dawley rats inflicted with 30% TBSA and the underlying mechanisms. We found that ITF significantly stimulated intestinal glutamine transport in burned rats. Mechanistically, ITF enhanced autophagy, reduces endoplasmic reticulum stress (ERS), and alleviates the impaired PDI, ASCT2, and B0AT1 in IECs and BBMVs after burn injury likely through AMPK activation. Therefore, ITF may protect intestinal epithelial cells from burn-induced injury through improving glutamine transport by alleviating ERS.

Glucose Control in Severely Burned Patients Using Metformin: An Interim Safety and Efficacy Analysis of a Phase II Randomized Controlled Trial

OBJECTIVE

To determine whether metformin can achieve glucose control no worse than insulin (noninferiority) without the danger of hypoglycemia (superiority). In addition, to assess whether metformin has any additional effects on lipolysis and inflammation that will enhance burn recovery (superiority).

SUMMARY BACKGROUND DATA

Hyperglycemia and insulin resistance after burn injury are associated with increased morbidity and mortality. Insulin administration improves postburn infections, severity of sepsis, and morbidity, but also causes a 4-5-fold increase in hypoglycemia, which is associated with a 9-fold increase in mortality.

METHODS

Severely burned adult patients with burns over 20% total body surface area (TBSA) burn were prospectively randomized in this Phase II clinical trial to either metformin or insulin (standard of care) treatment. Primary outcomes were glucose levels and incidence of hypoglycemia. Secondary outcomes included glucose and fat metabolism, and clinical outcomes.

RESULTS

Forty-four patients were enrolled in this Phase II clinical trial, 18 metformin and 26 insulin patients. Demographics, burn size, concomitant injuries, and mortality were comparable between both groups. Metformin controlled blood glucose as equally as insulin with no difference between the 2 treatment groups, P > 0.05. While there was a 15% incidence of hypoglycemia in the insulin group, there was only 1 mild hypoglycemic episode (6%) in the metformin group, P < 0.05. Oral glucose tolerance tests at discharge revealed that metformin significantly improved insulin sensitivity, P < 0.05. Furthermore, metformin had a strong antilipolytic effect after burn injury when compared with insulin and was associated with significantly reduced inflammation, P < 0.05.

CONCLUSIONS

Metformin decreases glucose equally as effective as insulin without causing hypoglycemia, with additional benefits including improved insulin resistance and decreased endogenous insulin synthesis when compared with insulin controls. These results indicate that metformin is safe in burn patients and further supports the use of metformin in severely burned patients for postburn control of hyperglycemia and insulin resistance.

Burn plus lipopolysaccharide augments endoplasmic reticulum stress and NLRP3 inflammasome activation and reduces PGC-1α in liver

Extensively burned patients often suffer from sepsis (especially caused by Pseudomonas aeruginosa), which may prolong metabolic derangement, contribute to multiple organ failure, and increase mortality. The molecular and cellular mechanisms of such infection-related metabolic derangement and organ dysfunction are unclear. We have previously shown that severely burned patients have significant and persisting hepatic endoplasmic reticulum (ER) stress. We hypothesized that ER stress and the unfolded protein response correlate with NOD-like receptor, pyrin domain containing 3 (NLRP3) inflammasome activation in burn. These may trigger profound metabolic changes in the liver, which form the pathological basis of liver damage and liver dysfunction after burn injury. A two-hit rat model was established by a 60% total body surface area scald burn and intraperitoneal injection of P. aeruginosa-derived lipopolysaccharide (LPS) 3 days after burn. One day later, animals were killed, and liver tissue samples were collected for gene expression and protein analysis of NLRP3 inflammasome activation, ER stress, and glucose and lipid metabolism. Liver damage was assessed by plasma markers (alanine aminotransferase and aspartate aminotransferase) and liver immunohistochemical analysis. Our results showed that burn injury and LPS injection induced inflammasome activation in liver and augmented hepatic ER stress and liver damage. Although there was an increased metabolic demand after burn, hepatic NLRP3 inflammasome activation corresponded to inhibition of PGC-1α (peroxisome proliferator-activated receptor γ-coactivator 1α) and its upstream regulators protein kinase A catalyst unit, AMP-activated protein kinase α, and sirtuin-1 may provide a mechanism for the enhanced metabolic derangement after major burn injury plus sepsis. In conclusion, burn + LPS augments inflammasome activation and ER stress in liver, which in turn contribute to postburn metabolic derangement.

Animal models in burn research

Burn injury is a severe form of trauma affecting more than 2 million people in North America each year. Burn trauma is not a single pathophysiological event but a devastating injury that causes structural and functional deficits in numerous organ systems. Due to its complexity and the involvement of multiple organs, in vitro experiments cannot capture this complexity nor address the pathophysiology. In the past two decades, a number of burn animal models have been developed to replicate the various aspects of burn injury, to elucidate the pathophysiology, and to explore potential treatment interventions. Understanding the advantages and limitations of these animal models is essential for the design and development of treatments that are clinically relevant to humans. This review aims to highlight the common animal models of burn injury in order to provide investigators with a better understanding of the benefits and limitations of these models for translational applications. While many animal models of burn exist, we limit our discussion to the skin healing of mouse, rat, and pig. Additionally, we briefly explain hypermetabolic characteristics of burn injury and the animal model utilized to study this phenomena. Finally, we discuss the economic costs associated with each of these models in order to guide decisions of choosing the appropriate animal model for burn research.