Susannah E. Nicholson

Development of a sleeve gastrectomy weight loss model in obese Zucker rats.

BACKGROUND Obesity promotes the development of diabetes and cardiovascular disease. The most effective weight loss treatment is bariatric surgery, but results greatly vary depending on the procedure. Sleeve gastrectomy (SG) has recently emerged as a reduced risk weight loss procedure for super obese patients. However, the mechanism of weight loss from SG and its effects on obesity-induced complications are yet to be determined. Our goal was to develop an experimental model of SG in genetically obese rats. MATERIALS AND METHODS Male obese Zucker rats (400-500 g, leptin-insensitive) were anesthetized with isoflurane. After a midline laparotomy, the stomach was clamped, the greater curvature was excised, and a triple suture line was used to close the gastric remnant. Sham rats underwent laparotomy only. Metabolic parameters were followed for 14 d after surgery. RESULTS Caloric intake and body weight decreased in SG rats over 14 d by 98 +/- 10 kcal/d and 74 +/- 14 g, respectively. Blood total cholesterol levels were lower in rats that lost weight. Furthermore, blood glucose levels were lower in rats that lost weight. Active ghrelin levels were unchanged in SG rats 14 d after surgery. CONCLUSIONS These results show that SG promotes weight loss in obese Zucker rats. Furthermore, SG-induced weight loss is accompanied by improved plasma cholesterol and glucose profile. However, SG does not promote a prolonged decrease in ghrelin levels. These results suggest that SG is an effective weight loss procedure in leptin insensitivity to improve the lipid profile and decrease insulin resistance and these effects might be independent of changes in ghrelin levels.

Transfusion-related acute lung injury in a rat model of trauma-hemorrhage.

BACKGROUND Major trauma often causes hemorrhage and predisposes to transfusion-related acute lung injury (TRALI). TRALI is a leading cause of transfusion-related deaths; however, its pathophysiology is uncertain. In the existing two-event models of TRALI, infection (lipopolysaccharide injection) is followed by the infusion of aged blood products. Our objective was to develop a trauma-relevant two-event model of TRALI by examining the effect of aged packed red blood cells (PRBC) on lung injury in rats with trauma-hemorrhage. METHODS Male Lewis rats were used. Rat PRBC were prepared similar to human PRBC. Recipients were implanted with femoral arterial and venous catheters (isoflurane anesthesia) and then subjected to 30% controlled arterial hemorrhage after 16-hour recovery. After a 60-minute shock period, rats were resuscitated with crystalloid and PRBC (0-35 days old; 3:1 ratio) and followed for up to 6 hours. Lung edema was evaluated by Evans blue dye (EBD), protein, and cytokine-induced neutrophil chemoattractant-1 (CINC-1) accumulation in bronchoalveolar lavage fluid, and arterial blood gases were measured (iSTAT). RESULTS CINC-1 levels increased over time in our PRBC stored for over 21 days. Transfusion survival was reduced, and Evans blue dye, protein, and CINC-1 accumulation in bronchoalveolar lavage fluid were increased in rats transfused with 28-day-old and 35-day-old PRBC compared with the 0-day group. Arterial PO2 and O2 saturation were decreased in rats transfused with 28-day-old and 35-day-old PRBC. However, pH and PCO2 were not different between groups. CONCLUSIONS These results suggest that transfusion of 28-day-old and 35-day-old PRBC reliably promotes lung edema in a rat model of catheter surgery and hemorrhage. We propose that this model can be used as a trauma-relevant two-event model of TRALI.

Liver Dysfunction by Model for End-Stage Liver Disease Score Improves Mortality Prediction in Injured Patients With Cirrhosis

BACKGROUND Cirrhosis is associated with poor outcomes in the trauma setting. We aimed to evaluate the utility of Model for End-Stage Liver Disease (MELD) in assessing additional mortality risk in trauma patients with cirrhosis. METHODS Injured patients with liver dysfunction were identified by hospital and trauma registry query. Presence of cirrhosis was confirmed by laparotomy, biopsy, or imaging. MELD classification, Child-Turcotte-Pugh (CTP) classification, Injury Severity Score (ISS), and Trauma ISS (TRISS) were recorded, and the primary outcome variable was hospital mortality. We assessed the validity of the four scoring systems in prediction of mortality, individually and in combinations, by comparing the areas under receiver operating characteristic curves (AUC), which is the probability, for scores that increase with the risk of death that a randomly chosen deceased subject will score higher than a randomly chosen living subject. RESULTS A total of 163 patients with confirmed cirrhosis were included. ISS (AUC = 0.849, p < 0.001) and TRISS (AUC = 0.826, p < 0.001) were the strongest predictors of mortality. MELD (AUC = 0.725) was not a significantly stronger predictor of mortality than CTP (AUC = 0.639; p = 0.38). ISS + MELD (AUC = 0.891) and ISS + CTP (AUC = 0.897) were stronger predictors than ISS alone (AUC = 0.849; p < 0.001) for both. The MELD score was more available from the records than the CTP score (91.4% vs. 75.5%). CONCLUSION In trauma patients with cirrhosis, a score that evaluates the degree of liver dysfunction enhances the ability of ISS alone to predict mortality. The MELD score is more readily available than the CTP score for the prediction of mortality in trauma patients.

Damage-associated molecular patterns (DAMPs) released after burn are associated with inflammation and monocyte activation

Burns are associated with activation of the innate immunity that can contribute to complications. Damage-associated molecular patterns (DAMPs) released after tissue injury play a critical role in the activation of the innate immunity, which appears to be mediated via toll-like receptors (TLRs). Previous findings have shown that TLRs and TLR-mediated responses are up-regulated after burn. Nonetheless, it is unclear what impact burn has on circulating levels of DAMPs. To study this, male C57BL/6 mice were subjected to a major burn or sham procedure. Three hours to 7days thereafter, plasma was collected and assayed for the representative DAMPs (i.e., HMGB1, cytochrome C, DNA and S100A) and extracellular cleavage products (fibronectin and hyaluronan). HMGB1, cytochrome C, fibronectin and hyaluronan levels were elevated in a time-dependent manner after burn as compared to sham levels. A significant elevation in TNF-α, IL-6 and IL-10 cytokine plasma levels was also found after burn. All cytokine levels were increased as early as 3h and remained elevated up to 24h. Circulating CD11b+ monocytes were increased at 24h after burn and showed increased expression of TLR-2. In conclusion, these findings support the concept that burn-induced elevations in circulating DAMPs are in part responsible for monocyte activation and the development of inflammatory complications under such conditions and warrants further investigation.

Dermal γδ T-cells can be activated by mitochondrial damage-associated molecular patterns

Background Gamma delta T-cells have been shown to be important to the early immunoinflammatory response to injury, independent of infection. This unique T-cell population acts to regulate cell trafficking and the release of cytokines and growth factors. We propose this sterile inflammatory response is in part associated with damage associated molecular patterns (DAMPs) generated by major injury, such as burn, and mediated via toll-like receptors (TLRs). It is unknown whether DAMPs can activate resident γδ T-cells that reside in skin. Methods Gamma delta T-cells were isolated from the skin of male C57BL/6 mice by enzymatic digestion. Mitochondrial DAMPs (MTDs) were generated from mitochondria isolated from mouse livers by sonication and centrifugation. Dermal γδ T-cells were incubated with MTDs (0–500 μg/ml) for 24 hr and cells and supernatants were collected for analysis. Results MTDs activated dermal γδ T-cells, as evidenced by increased TLR2 and TLR4 expression following in vitro exposure. MTDs also induced the production of inflammatory cytokines (IL-1β, IL-6), and growth factors (PDGF and VEGF) by γδ T-cells. Conclusions These findings herein support the concept that MTDs released after tissue/cellular injury are capable of activating dermal γδ T-cells. We propose that the activation of this unique T-cell population is central in the initiation of sterile inflammation and also contributes to the subsequent healing processes.

Compensatory reserve index: Performance of a novel monitoring technology to identify the bleeding trauma patient

Introduction: Hemorrhage is one of the most substantial causes of death after traumatic injury. Standard measures, including systolic blood pressure (SBP), are poor surrogate indicators of physiologic compromise until compensatory mechanisms have been overwhelmed. Compensatory Reserve Index (CRI) is a novel monitoring technology with the ability to assess physiologic reserve. We hypothesized CRI would be a better predictor of physiologic compromise secondary to hemorrhage than traditional vital signs. Methods: A prospective observational study of 89 subjects meeting trauma center activation criteria at a single level I trauma center was conducted from October 2015 to February 2016. Data collected included demographics, SBP, heart rate, and requirement for hemorrhage-associated, life-saving intervention (LSI) (i.e., operation or angiography for hemorrhage, local or tourniquet control of external bleeding, and transfusion >2 units PRBC). Receiver-operator characteristic (ROC) curves were formulated and appropriate thresholds were calculated to compare relative value of the metrics for predictive modeling. Results: For predicting hemorrhage-related LSI, CRI demonstrated a sensitivity of 83% and a negative predictive value (NPV) of 91% as compared with SBP with a sensitivity to detect hemorrhage of 26% (P < 0.05) and an NPV of 78%. ROC curves generated from admission CRI and SBP measures demonstrated values of 0.83 and 0.62, respectively. CRI identified significant hemorrhage requiring potentially life-saving therapy more reliably than SBP (P < 0.05). Conclusion: The CRI device demonstrated superior capacity over systolic blood pressure in predicting the need for posttraumatic hemorrhage intervention in the acute resuscitation phase after injury.

Comparison of Compensatory Reserve and Arterial Lactate as Markers of Shock and Resuscitation

BACKGROUND During traumatic hemorrhage, the ability to identify shock and intervene prior to decompensation is paramount to survival. Lactate is extremely sensitive to shock and its clearance has been demonstrated a useful gauge of shock and resuscitation status. Though lactate can be measured in the field, logistical constraints render it impractical in certain environments. The Compensatory Reserve represents a new clinical measurement reflecting the remaining capacity to compensate for hypoperfusion. We hypothesized the compensatory reserve index (CRI) would be an effective surrogate marker of shock and resuscitation compared to lactate. METHODS The CRI device was placed on consecutive patients meeting trauma center activation criteria and remained on the patient until discharge, admission, or transport to operating suite. All subjects had a lactate level measured as part of their routine admission metabolic analysis. Time-corresponding CRI and lactate values were matched in regards to initial and subsequent lactate levels. Mean time from lactate sample collection to data availability in the electronic medical record was calculated. Predictive capacity of CRI and lactate in predicting hemorrhage was determined by receiver-operative characteristic curve analysis. Correlation analysis was performed to determine if any association existed between changing CRI and lactate values. RESULTS Receiver-operator characteristic (ROC) curves were generated and area under the curve was 0.8052 and 0.8246 for CRI and lactate, respectively. There was no significant difference in each parameters ability to predict hemorrhage (p= 0.8015). The mean duration from lactate sample collection to clinical availability was 44 minutes while CRI values were available immediately. Analysis of the concomitant change in serial CRI and lactate levels revealed a Spearmans correlation coefficient of -0.73 (p < 0.01). CONCLUSION CRI performed with equivalent predictive capacity to lactate with respect to identifying initial perfusion status associated with hemorrhage and subsequent resuscitation. LEVEL OF EVIDENCE II.BACKGROUND During traumatic hemorrhage, the ability to identify shock and intervene before decompensation is paramount to survival. Lactate is extremely sensitive to shock, and its clearance has been demonstrated a useful gauge of shock and resuscitation status. Though lactate can be measured in the field, logistical constraints render it impractical in certain environments. The compensatory reserve represents a new clinical measurement reflecting the remaining capacity to compensate for hypoperfusion. We hypothesized the compensatory reserve index (CRI) would be an effective surrogate marker of shock and resuscitation compared to lactate. METHODS The CRI device was placed on consecutive patients meeting trauma center activation criteria and remained on the patient until discharge, admission, or transport to operating suite. All subjects had a lactate level measured as part of their routine admission metabolic analysis. Time-corresponding CRI and lactate values were matched in regards to initial and subsequent lactate levels. Mean time from lactate sample collection to data availability in the electronic medical record was calculated. Predictive capacity of CRI and lactate in predicting hemorrhage was determined by receiver-operator characteristic curve analysis. Correlation analysis was performed to determine if any association existed between changing CRI and lactate values. RESULTS Receiver-operator characteristic (ROC) curves were generated and area under the curve was 0.8052 and 0.8246 for CRI and lactate, respectively. There was no significant difference in each parameter’s ability to predict hemorrhage (p = 0.8015). The mean duration from lactate sample collection to clinical availability was 44 minutes whereas CRI values were available immediately. Analysis of the concomitant change in serial CRI and lactate levels revealed a Spearman’s correlation coefficient of −0.73 (p < 0.01). CONCLUSION CRI performed with equivalent predictive capacity to lactate with respect to identifying initial perfusion status associated with hemorrhage and subsequent resuscitation. LEVEL OF EVIDENCE Diagnostic, Level II.

The Cutaneous Microbiome and Wounds: New Molecular Targets to Promote Wound Healing

The ecological community of microorganisms in/on humans, termed the microbiome, is vital for sustaining homeostasis. While culture-independent techniques have revealed the role of the gut microbiome in human health and disease, the role of the cutaneous microbiome in wound healing is less defined. Skin commensals are essential in the maintenance of the epithelial barrier function, regulation of the host immune system, and protection from invading pathogenic microorganisms. In this review, we summarize the literature derived from pre-clinical and clinical studies on how changes in the microbiome of various acute and chronic skin wounds impact wound healing tissue regeneration. Furthermore, we review the mechanistic insights garnered from model wound healing systems. Finally, in the face of growing concern about antibiotic-resistance, we will discuss alternative strategies for the treatment of infected wounds to improve wound healing and outcomes. Taken together, it has become apparent that commensals, symbionts, and pathogens on human skin have an intimate role in the inflammatory response that highlights several potential strategies to treat infected, non-healing wounds. Despite these promising results, there are some contradictory and controversial findings from existing studies and more research is needed to define the role of the human skin microbiome in acute and chronic wound healing.

A Review of Traumatic Brain Injury and the Gut Microbiome: Insights into Novel Mechanisms of Secondary Brain Injury and Promising Targets for Neuroprotection

The gut microbiome and its role in health and disease have recently been major focus areas of research. In this review, we summarize the different ways in which the gut microbiome interacts with the rest of the body, with focus areas on its relationships with immunity, the brain, and injury. The gut–brain axis, a communication network linking together the central and enteric nervous systems, represents a key bidirectional pathway with feed-forward and feedback mechanisms. The gut microbiota has a central role in this pathway and is significantly altered following injury, leading to a pro-inflammatory state within the central nervous system (CNS). Herein, we examine traumatic brain injury (TBI) in relation to this axis and explore potential interventions, which may serve as targets for improving clinical outcomes and preventing secondary brain injury.

Polytrauma independent of therapeutic intervention alters the gastrointestinal microbiome

BACKGROUND This study characterizes the gastrointestinal (GI) microbiome in a pre-clinical polytrauma hemorrhage model. METHODS Rats (n = 6) were anesthetized, hemorrhaged 20% of their blood volume, and subjected to a femur fracture and crush injuries to the small intestine, liver, and limb skeletal muscle without resuscitation. Fecal samples were collected pre-injury and 2 h post-injury. Purified DNA from the samples underwent 16s rRNA sequencing for microbial quantification. Bacterial diversity analysis and taxonomic classification were performed. RESULTS Following injury, the gut microbial composition was altered with a shift in beta diversity and significant differences in the relative abundance of taxa. The relative abundance of the families Lachnospiraceae and Mogibacteriaceae was increased at 2 h, while Barnesiellaceae and Bacteroidaceae were decreased. Alpha diversity was unchanged. CONCLUSIONS The GI microbiome is altered in rats subjected to a polytrauma hemorrhage model at 2 h post-injury in the absence of antibiotics or therapeutic interventions.