In situ metabolic flux analysis to quantify the liver metabolic response to experimental burn injury

Abstract

Trauma such as burns induces a hypermetabolic response associated with altered central carbon and nitrogen metabolism. The liver plays a key role in these metabolic changes; however, studies to date have evaluated the metabolic state of liver using ex vivo perfusions or isotope labeling techniques targeted to specific pathways. Herein, we developed a unique mass balance approach to characterize the metabolic state of the liver in situ, and used it to quantify the metabolic changes to experimental burn injury in rats. Rats received a sham (control uninjured), 20% or 40% total body surface area (TBSA) scald burn, and were allowed to develop a hypermetabolic response. One day prior to evaluation, all animals were fasted to deplete glycogen stores. Four days post-burn, blood flow rates in major vessels of the liver were measured, and blood samples harvested. We combined measurements of metabolite concentrations and flow rates in the major vessels entering and leaving the liver with a steady-state mass balance model to generate a quantitative picture of the metabolic state of liver. The main findings were: (1) Sham-burned animals exhibited a gluconeogenic pattern, consistent with the fasted state; (2) the 20% TBSA burn inhibited gluconeogenesis and exhibited glycolytic-like features with very few other significant changes; (3) the 40% TBSA burn, by contrast, further enhanced gluconeogenesis and also increased amino acid extraction, urea cycle reactions, and several reactions involved in oxidative phosphorylation. These results suggest that increasing the severity of injury does not lead to a simple dose-dependent metabolic response, but rather leads to qualitatively different responses.

Resuscitation of Ischemic Donor Livers with Normothermic Machine Perfusion: A Metabolic Flux Analysis of Treatment in Rats

“…Note that it was previously demonstrated that in this model of rat DCD livers, 1 hr WI livers are not transplantable (0% survival by day 4 post transplant), however treatment by the NMP system also employed in this work increases the success to 100% (1 month post-transplant) [6]. Where necessary for comparison, in vivo values for rats were obtained and reported from another study [24].…”

Machine perfusion enhances hepatocyte isolation yields from ischemic livers

“…As perfusate viscosity increased, portal pressures increased and flow rates decreased. WE, with the lowest viscosity, approached rat physiological flow rates of 1.8 ml/min/g liver [37], averaging 1.4±0.08 ml/min/g liver with portal pressures averaging 10±1.8 cmH 2 O. Lower average flow rates of 1.2±0.03 ml/min/g liver in the higher-viscosity Lifor perfusate produced similar average portal pressures of 12±0.5 cmH 2 O. Vasosol and UW, with the highest viscosities, resulted in significantly higher average portal pressures of 16±0.8 cmH 2 O and 18±2.0 cmH 2 O respectively when average flow rates of 1.0±0.05 ml/min/g liver and 1.0±0.01 ml/min/g liver respectively were used to ensure adequate oxygenation.…”

Kupffer Cell p38 Mitogen-Activated Protein Kinase Signaling Drives Postburn Hepatic Damage and Pulmonary Inflammation When Alcohol Intoxication Precedes Burn Injury

“…Animal studies suggest hepatic derangement is dependent on the size of the burn with a threshold beyond which a qualitatively different response occurs (23). Work from our lab and others indicates that the presence of alcohol intoxication at the time of injury lowers the size of burn required to cause liver damage (10, 15, 24), though the mechanisms of how this ensues is currently unknown.…”