-Metabolic staging after trauma/hemorrhagic shock is a key driver of acidosis and directly relates to hypothermia and coagulopathy. Metabolic responses to trauma/hemorrhagic shock have been assayed through classic biochemical approaches or NMR, thereby lacking a comprehensive overview of the dynamic metabolic changes occurring after shock. Sprague-Dawley rats underwent progressive hemorrhage and shock. Baseline and postshock blood was collected, and late hyperfibrinolysis was assessed (LY30 Ͼ3%) in all of the tested rats. Extreme and intermediate time points were collected to assay the dynamic changes of the plasma metabolome via ultra-high performance liquid chromatography-mass spectrometry. Sham controls were used to determine whether metabolic changes could be primarily attributable to anesthesia and supine positioning. Early hemorrhage-triggered metabolic changes that built up progressively and became significant during sustained hemorrhagic shock. Metabolic phenotypes either resulted in immediate hypercatabolism, or late hypercatabolism, preceded by metabolic deregulation during early hemorrhage in a subset of rats. Hemorrhagic shock consistently promoted hyperglycemia, glycolysis, Krebs cycle, fatty acid, amino acid, and nitrogen metabolism (urate and polyamines), and impaired redox homeostasis. Early dynamic changes of the plasma metabolome are triggered by hemorrhage in rats. Future studies will determine whether metabolic subphenotypes observed in rats might be consistently observed in humans and pave the way for tailored resuscitative strategies. hemorrhagic shock; mass spectrometry; metabolomics; plasma; trauma DESPITE DECADES OF ADVANCES in prehospital care, trauma remains the leading cause of death for individuals under the age of 40 (36). As much as 40% of injury-related mortality is attributed to uncontrollable hemorrhage (36), which in both civilian and military settings is the leading preventable cause of death after injury (40). Conspicuous factors associated with early mortality in trauma patients include trauma-induced coagulopathy, hypothermia, and metabolic acidosis, a series of mechanisms referred to as the "bloody vicious cycle" and later renamed as the "lethal triad" (14). These concepts laid the foundation for "damage control surgery", an approach aimed at minimizing operating time as to control sources of significant bleeding and gastrointestinal contamination, while prioritizing early management of coagulopathy, hypothermia, and metabolic acidosis (46).Early descriptions of metabolic responses to trauma were documented by Cuthbertson, who characterized two distinct phases: the "ebb" and the "flow" (9). The former corresponds to an early hypometabolic state that may serve a protective role aimed at reducing posttraumatic energy depletion. The latter is accompanied by an increased metabolic rate (including increased energy expenditure and oxygen consumption) (14,18,24,29). Other overlapping stages have been described over the years, such as the "ischemia-reperfusion," "leukocytic," and ...

Background Metabolomic investigations have consistently reported succinate accumulation in plasma after critical injury. Succinate receptors have been identified on numerous tissues, and succinate has been directly implicated in post-ischemic inflammation, organ dysfunction, platelet activation and the generation of reactive oxygen species, which may potentiate morbidity and mortality risk to patients. Metabolic flux (heavy isotope labeling) studies demonstrate that glycolysis is not the primary source of increased plasma succinate during protracted shock. Glutamine is an alternative parent substrate for ATP generation during anaerobic conditions; a biochemical mechanism that ultimately supports cellular survival but produces succinate as a catabolite. We hypothesize that succinate accumulation during hemorrhagic shock is driven by glutaminolysis. Methods Sprague-Dawley rats were subjected to hemorrhagic shock for 45 min (Shock, n=8), and compared to normotensive shams (Sham, n=8). At 15 min, animals received intravenous injection of 13C515N2-glutamine solution (iLG). Blood, brain, heart, lung and liver tissues were harvested at defined time points. Labeling distribution in samples was determined by ultra high pressure liquid chromatography-mass spectrometry (UHPLC-MS) metabolomic analysis. Repeated measures ANOVA with Tukey comparison determined significance of relative fold-change in metabolite level from baseline. Results Hemorrhagic shock instigated succinate accumulation in plasma and lungs tissues (8.5 vs. 1.1 fold increase plasma succinate level from baseline, Shock vs. Sham, p=0.001; 3.2 fold higher succinate level in lung tissue, Shock vs. Sham, p=0.006). Metabolomic analysis identified labeled glutamine and labeled succinate in plasma (p=0.002) and lung tissue (p=0.013), confirming glutamine as the parent substrate. Kinetic analyses in shams showed constant total levels of all metabolites without significant change due to iLG. Conclusion Glutamine metabolism contributes to increased succinate concentration in plasma during hemorrhagic shock. The glutaminolytic pathway is implicated as a therapeutic target to prevent the contribution of succinate accumulation in plasma and the lung to post-shock pathogenesis.

Key Points• In vivo tracing of 13 C 15 N-glutamine reveals that glutaminolysis is an essential contributor to RBC metabolism following HS.• Inhibition of glutaminolysis impairs transamination reactions and GSH synthesis, promoting early mortality in hemorrhaged rats.