Improvements of postburn renal function by early enteral feeding and their possible mechanisms in rats

Kinetics of Inflammatory Mediators in the Immune Response to Burn Injury: Systematic Review and Meta-Analysis of Animal Studies

Burns are often accompanied by a dysfunctional immune response, which can lead to systemic inflammation, shock, and excessive scarring. The objective of this study was to provide insight into inflammatory pathways associated with burn-related complications. Because detailed information on the various inflammatory mediators is scattered over individual studies, we systematically reviewed animal experimental data for all reported inflammatory mediators. Meta-analyses of 352 studies revealed a strong increase in cytokines, chemokines, and growth factors, particularly 19 mediators in blood and 12 in burn tissue. Temporal kinetics showed long-lasting surges of proinflammatory cytokines in blood and burn tissue. Significant time-dependent effects were seen for IL-1β, IL-6, TGF-β1, and CCL2. The response of anti-inflammatory mediators was limited. Burn technique had a profound impact on systemic response levels. Large burn size and scalds further increased systemic, but not local inflammation. Animal characteristics greatly affected inflammation, for example, IL-1β, IL-6, and TNF-α levels were highest in young, male rats. Time-dependent effects and dissimilarities in response demonstrate the importance of appropriate study design. Collectively, this review presents a general overview of the burn-induced immune response exposing inflammatory pathways that could be targeted through immunotherapy for burn patients and provides guidance for experimental set-ups to advance burn research.

Evaluation of toxicological impacts on Sprague-Dawley rat by successively low dose of aflatoxin B1

BACKGROUND

Aflatoxins (AFs) are a group of potent mycotoxins that frequently pollute agro-products and animal feeds. For complex reasons, the regulatory limits of AFs differ from nation to nation. In this study, feedstuffs contaminated with various concentrations of aflatoxin B1 (AFB1) corresponding to AF regulatory limits of major agro-product importing and exporting nations were tested in Sprague-Dawley rats, and the toxicological results were evaluated.

RESULTS

During the trial period, no poisoning behavior was observed and no animals died. No significant differences in body weight were observed between AFB1-contaminated and control rats. However, various negative impacts on liver and kidney functions were observed in AFB1-contaminated groups, and these negative impacts were positively correlated with AFB1 concentrations. At concentrations of 4-50 µg kg(-1) , AFB1 tolerance was observed for the liver after 15 days of testing, but this tolerance was not observed for the kidney.

CONCLUSION

Low concentrations of AFB1 still induced obvious toxicological impacts on Sprague-Dawley rats, and the negative effects were aggravated by increasing the AFB1 dose and feeding time. Therefore strict AF regulatory limits are suggested for food safety administration, especially for the low-income nations with higher hepatitis B virus prevalence.

Electroacupuncture improves burn-induced impairment in gastric motility mediated via the vagal mechanism in rats

BACKGROUND

Delayed gastric emptying (GE) is common in patients with severe burns. This study was designed to investigate effects and mechanisms of electroacupuncture (EA) on gastric motility in rats with burns.

METHODS

Male rats (intact and vagotomized) were implanted with gastric electrodes, chest and abdominal wall electrodes for investigating the effects of EA at ST-36 (stomach-36 or Zusanli) on GE, gastric slow waves, autonomic functions, and plasma interleukin 6 (IL-6) 6 and 24 h post severe burns.

KEY RESULTS

(i) Burn delayed GE (P < 0.001). Electroacupuncture improved GE 6 and 24 h post burn (P < 0.001). Vagotomy blocked the EA effect on GE. (ii) Electroacupuncture improved burn-induced gastric dysrhythmia. The percentage of normal slow waves was increased with EA 6 and 24 h post burn (P = 0.02). (iii) Electroacupuncture increased vagal activity assessed by the spectral analysis of heart rate variability (HRV). The high-frequency component reflecting vagal component was increased with EA 6 (P = 0.004) and 24 h post burn (P = 0.03, vs sham-EA). (iv) Electroacupuncture attenuated burn-induced increase in plasma IL-6 at both 6 (P = 0.03) and 24 h post burn (P = 0.003).

CONCLUSIONS & INFERENCES

Electroacupuncture at ST-36 improves gastric dysrhythmia and accelerates GE in rats with burns. The improvement seems to be mediated via the vagal pathway involving the inflammatory cytokine IL-6.

Nutritional and pharmacological modulation of the metabolic response of severely burned patients: review of the literature (part 1)

Severe burn patients are some of the most challenging critically ill patients, with an extreme state of physiological stress and an overwhelming systemic metabolic response. Increased energy expenditure to cope with this insult necessitates mobilization of large amounts of substrate from fat stores and active muscle for repair and fuel, leading to catabolism. The hypermetabolic response can last for as long as nine months to one year after injury and is associated with impaired wound healing, increased infection risks, erosion of lean body mass, hampered rehabilitation, and delayed reintegration of burn survivors into society. Reversal of the hypermetabolic response by manipulating the patient's physiological and biochemical environment through the administration of specific nutrients, growth factors, or other agents, often in pharmacological doses, is emerging as an essential component of the state of the art in severe burn management. Early enteral nutritional support, control of hyperglycaemia, blockade of catecholamine response, and use of anabolic steroids have all been proposed to attenuate hypermetabolism or to blunt catabolism associated with severe burn injury. The present study is a literature review of the proposed nutritional and metabolic therapeutic measures in order to determine evidence-based best practice. Unfortunately, the present state of our knowledge does not allow the formulation of clear-cut guidelines. Only general trends can be outlined which will certainly have some practical applications but above all will dictate future research in the field.

A comparison study between early enteral nutrition and parenteral nutrition in severe burn patients

This clinical study compares effects between enteral nutrition and parenteral nutrition in the early stage of severe burns. Nineteen cases of severe burn patients were divided randomly into total enteral nutrition group (TEN) and total parenteral nutrition group (TPN). Plasma motilin, malondialdehyde (MDA), superoxide dismutase (SOD), endotoxin, tumor necrosis factor (TNF), serum gastrin, diamine oxidase (DAO), and urine lactulose/mannitol ratio (L/M) was determined on post burn day (PBD) 1, 4, 8, 14, respectively. The results showed that serum gastrin, plasma motilin, and SOD were significantly higher in TEN than in TPN on PBD4, 8 (p<0.05-0.01). Plasma MDA was obviously lower in TEN than in TPN on PBD4, 8 (p<0.01). Plasma endotoxin was significantly lower in TEN than in TPN on PBD4, 8 (p<0.01). Plasma TNF were significantly lower in TEN than in TPN on PBD4, 8, 14 (p<0.01). The level of serum DAO and urine L/M ratio in TEN was obviously lower than in TPN on PBD4 and 8, respectively (p<0.05-0.01). A positive correlation between L/M and DAO, MDA, TNF (r=0.5822-0.7598, p<0.05-0.01), and a negative correlation between L/M and SOD (r=-0.7771, p<0.01), and a positive correlation between plasma endotoxin and TNF, MDA (r=0.9038 and 0.6705, p<0.05-0.01) were found. These results indicate that enteral nutrition was a more effective route to preserve gastrin secretion and motility of gastrointestinal tract, lower intestinal ischemia and reperfusion injury, reduce intestinal permeability, decrease plasma endotoxin and inflammatory mediators, and maintain mucosa barrier function. Whenever gastrointestinal function permits, enteral nutrition was superior to parenteral nutrition early after burn.

Early Enteral Nutrition Does Not Decrease Hypermetabolism Associated with Burn Injury

BACKGROUND

A prospective, randomized study was performed to compare the effects of early versus late enteral feeding on postburn metabolism.

METHODS

Burn patients were randomized to receive enteral feedings either within 24 hours (early) or 7 days (late) of injury. Basal energy expenditure (BEE) was calculated from Harris-Benedict equations and resting energy expenditure (REE) was obtained from indirect calorimetry. The average daily energy expenditure (DEE) was expressed as REE/BEE.

RESULTS

Average age, burn size, infections, and length of stay were similar between groups. Mortality between groups was similar (early, 28%; late, 38%) and not significantly influenced by inhalation injury. When controlled for percentage of total body surface area burn, inhalation injury, and age, the early group had an increased rather than decreased DEE, with a mean DEE calorie 0.17 more than the late group (p = 0.07).

CONCLUSION

Early enteral feeding does not decrease the average energy expenditure associated with burn injury.