PMC

The citric acid cycle and relevant metabolic contributions. Solid black arrows indicate primary pathway; dotted arrows indicate alternate pathways. αKg, α-ketoglutarate; ATP, adenosine triphosphate; NADH, nicotinamide adenine dinucleotide; 2HG, 2-hydroxyglutarate. (a) Aerobic metabolism under physiologic conditions. (b) During ischemia, glutaminolysis provides α-ketoglutarate to facilitate substrate-level phosphorylation and secure cellular survival. Succinate is produced as a catabolic product.

Batched MS-metabolomic analyses were performed on plasma samples from shock and sham models. (a) Schematic of isotopologue analysis following iLG identifying catabolic products of labeled ¹³C5-¹⁵N2-glutamine (M+5+2) metabolism. (b) Hypoxia-driven uncoupling of the electron transport chain prevents succinate metabolism to fumarate in order to facilitate substrate-level phosphorylation and generate ATP/NADH. (–)) M+X+Y, molecular ion peak + no. of (labeled) ¹³C + no. of (labeled) ¹⁵N

Batched MS-metabolomic analyses were performed on homogenized brain, heart, liver and lung tissue collected after sacrifice from shock and sham models. (a) After 45 min of hemorrhagic shock, total succinate (M+0, blue) had accumulated in lung tissue. Total succinate levels were lower in shocked brain, heart and liver tissues when compared to sham controls. Fumarate and malate accumulated in all tissues after shock. (b) Isotopologue analysis identified labeled succinate in shocked lung tissue when compared to shams, but did not identify labeled (M+4, red) succinate in shocked liver tissue. (* p<0.05, ** p<0.001, n=8/group) M+X+Y, molecular ion peak + no. of (labeled) ¹³C + no. of (labeled) ¹⁵N

Batched MS-based metabolomic analyses were performed on plasma samples from shock and sham models. Baseline metabolic profiles were similar between groups. In shams, unlabeled (M+0, blue) metabolite levels remained in steady state for the duration of the experiment without significant change due to instrumentation or iLG, while hemorrhagic shock instigated broad metabolite accumulation. Plasma abundance of labeled glutamine (M+5+2, red) following iLG was consistent between models at all time points and demonstrated progressive metabolism. Shock generated labeled glutamate (M+5, red; M+5+1, green) and succinate (M+4, red) accumulation, but did not increase fumarate (M+4, red) or malate (M+4, red) abundance compared to sham. (*p<0.05, **p<0.001, n=8/group) M+X+Y, molecular ion peak + no. of (labeled) ¹³C + no. of (labeled) ¹⁵N