TABLE 3.

Results reported in the publications included by the systematic search

Article	Species	Injury definition	Renal function clinical markers	Additional damage markers	Results on metabolome
Rat
Andrianova et al. 2020 7	Rat	Serum creatinine (SCr) levels: “After IR, creatinine concentration increased in all animals, varying from 50 to 200–500 µM, indicating that IR caused AKI” Note: no thresholds given.	SCr (increase post‐IR)	—	Only measured acylcarnitines (ACs) and amino acids (AAs). After IR, we detected 34 metabolites in blood serum, whose levels significantly changed—concentration of 31 acylcarnitines increased, while the content of 3 AAs (tyrosine, tryptophan, and proline) dropped. The most significant changes were observed for malonylcarnitine, which demonstrated a sevenfold increase compared to control, glutarylcarnitine (fivefold increase), decadienoyl carnitine (fourfold increase), hydroxybutyrylcarnitine (fourfold increase), linoleylcarnitine (fourfold increase), and methylmalonylcarnitine (fourfold increase). Other acylcarnitines showed about a twofold increase. The serum levels of the tyrosine, tryptophan, and proline concentration dropped to 60%–70% of their content.
Choi et al. 2019 8	Rat	Not defined	—	—	Principal component analysis: Significant separation following cardiac arrest (CA) and following resuscitation. Citrate, a‐ketoglutarate, malate, fumarate, and succinate significantly changed in kidney after cardiopulmonary bypass (CPB) compared with control or CA. Individual metabolite changes: ‐The only amino acids that were unaffected by CA were glutamine, threonine, alanine, and valine, remaining measured amino acids were significantly decreased. Thirty minutes of CPB resuscitation resulted in even more dysregulation; all measured amino acids with the exception of glutamate, alanine, and valine were significantly decreased. ‐Thirty minutes of CPB resuscitation resulted in a significant decrease in linoleic and linolenic acids, while stearic acid returned to control levels. The general trend of lipids in the kidney is that they increase after ischemia, but either return to or fall below control levels after resuscitation. ‐The kidney shows variations in glycolytic and TCA cycle metabolites, such as a significant elevation in 3‐phosphoglycerate and oxoglutarate after 20 minutes of CA. However, CPB resuscitation resulted in a significant increase in citrate, oxoglutarate, succinate, fumarate, malate, and oxaloacetate. ‐The urea cycle metabolites were mostly altered after 30 min of CPB resuscitation in the kidney. ‐Arginine and proline were significantly decreased after CA, but after CPB, arginine, citrulline, ornithine, and proline were all decreased. Changes in acylcarnitine species: CA resulted in elevation in only AC 16:0 when compared with control. Resuscitation resulted in a decrease from CA in AC 2:0, AC 8:0, AC 10:0, AC 14:2, AC 16:1, AC 16:0, AC 18:2, and AC 18:1. AC species that were decreased after resuscitation were AC 6:0, AC 8:0, AC 10:0, AC 14:2, AC 14:1, AC 16:2, AC 16:1, AC 18:2, and AC 18:1. The kidney was unable to normalize ACs after resuscitation, resulting in a generally diminished lipid reserve after 30 min of CPB resuscitation. Pathway analysis: In kidney tissue following resuscitation, 46 pathways remained significantly altered compared with control, with nicotinate and nicotinamide metabolism, and phenylalanine metabolism having the lowest q values.
Duran et al. 1990 9	Rat	Not defined	BUN (no change post‐IR)	Kidney weight (increase post‐IR)	Only measured AAs: The plasma concentrations of AAs were indistinguishable from control. Cellular AAs post‐IR: glutamate, glycine, phenylalanine, and serine in cortical cell water (=derived from tissue) were decreased 3 h after ischemia, but those of the remaining 12 AAs were not different from control. Concentrations of glutamate and glycine had normalized 24 h after blood reflow, leaving only 4 AAs—arginine, phenylalanine, serine and threonine—at decreased concentration.
Gaudio et al. 1991 10	Rat	EM images of proximal tubule segments: “Following ischemia and 15 min of reperfusion, there were marked cellular alterations typical of ischemic injury.”	—	Histology	Forty‐five min of ischemia resulted in a significant fall in ATP levels. ATP levels had increased by only a small amount after 2h of reperfusion.
Huang et al. 2018 11	Rat	Not defined	SCr (increase post‐IR) Lactate (tissue and plasma levels increase post‐IR)	Histology	Metabolomics: ‐Palmitate, stearate, linoleate, 1‐monopalmitin, 2‐monopalmitin, 2‐monostearin, and cholesterol appeared to accumulate after 4 h followed by a reduction after 24 h IR. ‐Reduced glucose levels in both 4 h IR and 4 h control (4 h‐C) kidneys that were sustained in 24 h‐IR as compared to HC (healthy control). Glucose levels were unaltered in plasma of 4 h and 24 h operated animals. Lactate levels were increased in 24 h IR as compared to HC, and were also significantly elevated in the plasma of 4 h operated animals and even to a greater extent after 24 h. ‐Blood creatinine levels were higher in both 4 h and 24 h post‐IR. ‐Compensatory changes in metabolite levels in the uninjured organ of animals subjected to kidney IR, in particular after 24 h reperfusion: a strong elevation of urea and AMP in contralateral kidneys after 24 h post‐IR, which was not observed in the injured kidney counterpart. Adenosine, glutamic acid, and glycine levels were increased in a more prominent fashion in contralateral kidneys, particularly after 24 h. Citrate appeared to be elevated in all conditions as compared to control. ATP levels were significantly decreased in 24 h IR kidney tissue as compared to 24 h C and HC. Integrated analysis: Hierarchical cluster analysis revealed the existence of five phenotypes: (i) Decreased substrates in 4 h IR and/or 4 h C compared to HC and 24 h IR/C. This includes proteins involved in fatty acid (FA) biosynthesis (Acsl6, Acsl4), metabolites involved in energy metabolism (glucose and citric acid); (ii) Decreased substrates prevalently in 24 h IR compared to the other conditions. This group: adenosine, proteins involved oxidation and reduction reactions (Por), and enzyme that play role in the TCA cycle (Pdha1/1). (iii) Metabolites increased prevalently in 24 h C animals as compared to the other conditions. This includes free fatty acids (FFAs) (2‐monostearin, 2‐monopalmitin, and linoleate), non‐essential amino acids (glutamic acid and glycine), urea, AMP, and creatinine. (iv) Proteins and metabolites prevalently increased in 24 h IR including enzymes involved in oxidative phosphorylation (Ndufa6, Ndufv1, and Ndufs1), fatty acid binding protein (Fabp4), glycolysis enzyme (Hk1), and lactate. (v) Enzymes and metabolites elevated in 4 h IR and 4 h C such as glucose transporter (Slc5a1), FA transporter (CD36), components of oxidative phosphorylation (ND−1), detoxification enzymes (Adh5, Ugt2b15), mitochondrial biogenesis (Sirt2), FFA metabolism (Cpt1a, Acadsb, Echdc3, palmitate, stearate, and 1‐monopalmitin), and ketone metabolism (Oxct1).
Lan et al. 2016 12	Rat	IR injury was monitored by SCr and renal histology. Note: no thresholds given.	SCr (no data reported)	Histology	During reperfusion 3, 7, and 14 days after IR, lactate, and pyruvate concentrations in cortex and the outer stripe of outer medulla were increased relative to time controls.
Legouis et al. 2020 3	Rat	Not defined	—	—	Renal gluconeogenesis, selectively quantified by analysis of blood from the renal vein, was reduced in response to IR.
Lindhardt et al. 2020 13	Rat	Not defined	SCr (no control) BUN (no control) Urinary creatinine (no control)	—	The metabolism measured in vivo by product/pyruvate ratios showed a significant decrease in the ischemic kidney compared with the contralateral kidney when considering all metabolites (lactate, alanine, and bicarbonate).
Liu et al. 2012 14	Rat	BUN and SCr were two widely used indicators of kidney Injury. There were significant differences in SCr and BUN between the control and IR groups. Note: no thresholds given.	SCr (increase post‐IR) BUN (increase post‐IR)	—	‐Most important IR‐related metabolites are lysophospholipids and FFAs, including stearoyl‐glycerophosphocholine, eicosatrienoyl‐glycerophosphocholine, oleoyl‐glycerophosphocholine, palmitoyl‐glycerophosphocholine, linoleoyl‐glycerophosphocholine, linolenoyl lysolecithin, stearic acid, oleic acid, linoleic acid, arachidonic acid, and eicosapentaenoic acid. ‐Nitrotyrosine (oxidative product of tyrosine) significantly increased in the IR group. ‐Increased hydroxymethylphenidate after IR. ‐Carnitine and acetyl‐carnitine decreased during IR. ‐Saturated fatty acids and unsaturated fatty acids displayed different changes in the IR group. However, stearic acid made more contribution than polyunsaturated fatty acids (PUFAs) to discriminate between the IR and control.
Nielsen et al. 2017a 15	Rat	Functional kidney parameters showed consistent signs of renal IR injury with an elevated plasma creatinine level of 91% and a reduced creatinine clearance and BUN level of 44% and 30%, respectively, when comparing presurgery with postsurgery values. Note: no thresholds given.	SCr (increase post‐IR) BUN (increase post‐IR) Creatine clearance (decrease post‐IR) Urine output (non‐significant increase post‐IR)	Histology Body weight (non‐significant decrease post‐IR) Kidney weight (increase post‐IR)	An elevated malate/fumarate ratio of 339% in the ischemic kidneys compared to that in the contralateral kidney was found.
Nielsen et al. 2017b 16	Rat	We demonstrated that increased BUN and plasma creatinine occurred in both unilateral IR groups compared with sham‐operated rats. Together, this indicates that renal IR resulted in acute renal insufficiency. Note: no thresholds given.	SCr (increase post‐IR) BUN (increase post‐IR)	Renal KIM−1 and NGAL mRNA expression (increase post‐IR) Body weight (decrease post‐IR) Kidney weight (increase post‐IR (60 min ischemia))	Significant decrease of 18–25% in the pyruvate‐to‐lactate conversion in the 60‐min postischemic kidney compared with the contralateral kidneys and kidneys from sham‐operated rats. No reduction in pyruvate‐lactate turnover was observed in the 30‐min IR Group. The alanine‐to‐pyruvate and bicarbonate‐to‐pyruvate ratio similarly showed a decrease of 44% and 59%, respectively, in the postischemic kidney, no reduction in metabolite turnover was seen in the 30‐min IR Group. The lactate‐to‐bicarbonate ratio was significantly shifted toward anaerobic glycolysis in the 60‐min postischemic kidney by 44%. No statistical difference was found between alanine metabolism and aerobic glycolysis (alanine‐to‐bicarbonate ratio), but the lactate‐to‐alanine ratio was significantly increased by 25%, and a small increase in lactate‐to‐alanine ratio of 23% was also seen in the 30‐min IR group. Pyruvate‐to‐total carbon signal and a total carbon kidney fraction were calculated for each kidney of the sham‐operated and unilateral IR rats, which yielded a significantly elevated ratio of 6% for the 60‐min postischemic kidney. Increase in lactate in the 60‐min IR group of 178%, and no significant increase in the 30‐min group.
Nielsen et al. 2020 17	Rat	Not defined	SCr (increase post‐IR for longer ischemia, stable levels post‐IR for short ischemia, and [partially] recover 7 days post‐IR)	—	Acute alterations in the ischemic re‐perfused kidneys overall metabolic phenotype were seen between the ischemic/early perfusion stage (2 min) and after 1 hour of perfusion, showing a compensatory mechanism in the contralateral kidney 60 min after reperfusion. The acute change in the lactate‐to‐bicarbonate ratio 60 min after reperfusion was not correlated with the early signature 2 min after reperfusion. The acute metabolic reprogramming seen at 60 min was driven by postrelease compensation in the contralateral kidney as well as downregulation of the lactate‐to‐bicarbonate balance in the ischemic kidney. The in vivo response that was seen 24 hours and 7 days following ischemic injury showed a similar tendency toward a general reduction in the overall metabolism in the ischemic kidney as well as a compensatory increased anaerobic metabolism shown by increased lactate production when compared to the aerobic metabolism, shown by CO2 and HCO3 production. Both 20 min and 40 min ischemia in the kidney results in a tendency toward a metabolic reprogramming from 24 hours to 7 days, with a statistically significant shift observed in the 40 min group. The metabolic phenotype at 24 hours, with reduced lactate‐to‐bicarbonate ratio, is positively correlated with the lactate‐to‐bicarbonate ratio at 7 days. A positive correlation was found in the lactate‐to‐bicarbonate ratio between 24 hours and 7 days. While no such correlation was found between the perfusion stage (2 min) and 60 min. By looking at the 20 min and 40 min group, one group with a large variance covering the 30 min acute insult, we compared the overall metabolic pattern from the initial 2 min to 7 days between the ischemic and contralateral kidney. This combination shows a significant change already at 60 min which persists throughout the 7 days. These findings are supported by a tendency toward a correlation between the lactate‐to‐bicarbonate ratio.
Peto et al. 2018 18	Rat	Not defined	Lactate (blood lactate increase post‐IR and pH decrease)	—	‐Blood lactate concentration in parallel to pH increased by the end of the observed reperfusion period in all groups. In control group, the change was not significant, but in IR, where the largest rise was found, it was. ‐No significant change in glucose concentration.
Serkova et al. 2005 19	Rat	Graft function: clinical appearance, histology, SCr, and urine output. Note: no thresholds given.	SCr (increase post‐IR) Anuria	Histology Clinical appearance (behavior, fur, etc.) Body weight (no change post‐IR)	Tissue: ‐Cold storage in UW solution: significant increase in glycogen and other carbohydrates was observed at 24 and 42 hours of CI. The lactate concentration was greatly increased, up to 380% during CI. In the lipid extracts, a decrease in PUFAs was seen in CI groups versus native kidney. There were no significant differences in metabolic composition at the end of 24 and 42 hours of CIT. ‐Transplanted kidneys exposed to reperfusion for 24 hours demonstrated characteristic changes: most pronounced difference between the post‐IR and post‐I groups was the dramatic increase in allantoin. Allantoin concentrations were low in the native kidney and at the end of CI, but increased significantly after 24 h reperfusion. Stepwise logistic regression analysis revealed that from 30 metabolites quantified from kidney extracts, only two—allantoin and PUFA—were different among study groups. Blood: ‐In 6/8 animals in the native group, allantoin concentrations were below the limit of quantification for NMR. ‐ Allantoin peaks appeared in the blood in both CI groups following reperfusion. Allantoin concentrations were higher in transplanted rats with 42‐hour cold storage when compared with 24‐hour cold storage. ‐Trimethylamine oxide (TMAO) correlated well with CIT. TMAO concentration correlated well with elevated allantoin levels. ‐Uric acid concentrations were below the linear range for the assay.
Shen et al. 2017 20	Rat	Renal injury confirmed by histology: disrupted kidney structure.	—	Histology	‐All metabolites enriched in the biosynthesis of unsaturated fatty acids were augmented in IR group in contrast to the control group. ‐D‐glucose, lactic acid, and cholesterol were differentiated significantly between control and IR group.
Tani et al. 2019 21	Rat	Not defined	Lactate (tissue levels increase post‐IR) SCr (increase post‐IR) BUN (increase post‐IR)	—	‐Energy charge decreased upon ischemia, and increased upon reperfusion. ‐Total adenine nucleotide (TAN), ATP and ADP levels are decreased upon ischemia, and increased only slightly upon reperfusion. AMP showed hardly any difference between stationary state and ischemia, but decreased during reperfusion to a lower level. ‐Hypoxanthine, xanthine, and uric acid levels are high after ischemia, but return to baseline after reperfusion. ‐All groups in the ischemic state showed an increase in IMP level and a decrease in deoxyadenosine triphosphate (dATP) level, and a decrease in the adenine level after reperfusion. ‐TAN’ (the sum of all detectable purine metabolites excluding ATP, ADP, and AMP, thus including dATP, PRPP, adenosine, adenine, inosine, IMP, hypoxanthine, xanthine, and uric acid) increased during ischemia and dropped to approximately baseline after reperfusion again. ‐Drastic metabolic changes by the IR procedure: triphosphate compounds in purine/pyrimidine metabolism pathways, nicotinamide adenine dinucleotide (NAD+), uridine diphosphate (UDP)‐glucose, kynurenine, citrulline, and amino acids such as ornithine, isoleucine, leucine, and tryptophan. ‐Marked accumulation of hydrolysis products, such as lactate and ß‐hydroxybutyrate.
Trifillis et al. 1984 22	Rat	SCr and BUN were used as indices of renal function. Note: no thresholds given.	SCr (increase post‐IR) BUN (increase post‐IR)	Survival	1 h ischemia and variable reperfusion times: ATP levels after 1 h of clamping decreased significantly to 18% of control levels. Upon release of the clamp, ATP levels began to increase after 0.25 h of reflow. ATP concentrations finally returned to control levels after 24 h of reflow. ADP levels remained relatively unchanged. AMP levels doubled after 1 h of ischemia but promptly returned to control levels after 0.25 h of reflow. Therefore, changes in AXP levels paralleled those of ATP levels, that is, AXP levels were not fully restored to control levels until 24 h of reflow. The energy charge decreased to 50% of the control value after 1 h of ischemia but returned to control levels after 6 h of reflow. Lactate levels reached 13‐fold control levels after 1 h of clamping and remained significantly elevated until 24 h of reflow when they returned to control levels. Variable ischemia times and 24 h of reperfusion: 120 min of ischemia resulted in death within the 24‐h reflow period. SCr levels increased significantly after 60 and 90 min of ischemia followed by 24 h of reflow. In the left kidney, adenine nucleotides, lactate, and inorganic orthophosphate levels were restored essentially to control levels after 30 min of ischemia followed by 24 h of reflow. Adenine nucleotide levels were partially restored but remained significantly lower than control levels after 60 and 90 min of ischemia and 24 h of reflow. Lactate levels were restored to controls after 15–90 min of ischemia followed by 24 h of reflow. Inorganic orthophosphate and the phosphorylation state were significantly different from controls only after 60 min of ischemia followed by 24 h of reflow. Adenine nucleotide, lactate, and inorganic orthophosphate content of the right kidney were not significantly different from that of the left kidney at any time period studied, that is, the time course and magnitude of metabolite restoration following 24 h of reflow was the same in both kidneys.
Varga et al. 2019 23	Rat	Not defined	Lactate (serum levels increase post‐IR and pH decrease) SCr (increase post‐IR)	—	Lactate and potassium concentration significantly increased in IR (measurements after 120 min). IR decreased the pH.
Mouse
Beier et al. 2020 24	Mouse	Not defined	—	—	We found 30 metabolites elevated in IR. Among the uniquely increased metabolites in IR (compared to acute cellular rejection), the highest fold difference was observed for the lysine catabolite saccharopine. Also the downstream products 2‐aminoadipate and glutarate, but not the parent substrates lysine and α‐ketoglutarate, were increased in IR.
Chihanga et al. 2018 25	Mouse	SCr, urinary NGAL, urinary NGAL/urinary creatinine ratios, and urinary creatinine levels confirmed AKI 24 h post‐IR. Note: no thresholds given.	SCr (increase post‐IR) Urinary creatinine (decrease post‐IR)	Histology Urinary NGAL (increase post‐IR) Urinary NGAL/urinary creatinine (increase post‐IR)	‐Urinary concentrations of many metabolites before IR changed dramatically after IR. Cis‐aconitate, citrate, creatine, phosphocreatine, putrescine, sarcosine, succinate, taurine, n‐nitrosodimethylamine, trimethylamine, uracil, and trimethylamine N‐oxide, galactaric acid, guanine, and hippurate all decreased following IR. Nicotinamide‐n‐oxide, trigonelline, 2‐oxoglutarate, and 2‐oxoisocaproate were absent in urine following injury. Glucose, lactate, alanine, valine, and leucine had higher urine concentrations following IR. ‐NMR spectroscopy of plasma collected 24 h post‐IR indicated no new metabolites post‐IR except for creatinine. Metabolic profiling of kidney tissue extracts indicated no new metabolites following IR.
Cho et al. 2017 26	Mouse	There was a significant increase in acute tubular injury in the IR group compared to the sham group.	—	Histology	‐The levels of adenosine and 5'‐deoxy−5'‐methylthioadenosine were higher in IR‐injured kidney. IR‐injured kidney was characterized by decreased phosphatidylethanolamine (PE) 20:3/20:4, and betaine aldehyde levels in kidney samples, as well as increased cell membrane constituents. ‐Increased serum levels of fatty acids; in particular, 4,14‐dimethyl‐hexadecanoic acid, 15‐eicosenoic acid, 3,5‐dimethyl‐tetradecanoic acid, cis−8,11,14‐eicosatrienoic acid, and 3‐oxo−2‐pentyl‐cyclopentaneoctanoic acid. The acyl‐carnitines 2‐octenoylcarnitine and 2‐hydroxylauroyl‐carnitine were decreased in the urine and serum, respectively. Levels of arachidonic acid and cis−4,7,10,13,16,19‐docosahexaenoic were lower following IR than in the sham group.
a Chouchani et al. 2014 27	Mouse	Not defined	—	—	Increase in hypoxanthine and xanthine after ischemia. Succinate accumulation during ischemia, recovery to baseline after 5 min of reperfusion.
Fujii et al. 2019 28	Mouse	Transient ischemia for 10 min was sufficient to cause significant renal injury with increased NAG in urine and decreased creatinine clearance. No histological damage. Note: no thresholds given.	Creatinine clearance (decrease post‐IR)	Histology (note: no changes) Urinary NAG (increase post‐IR)	‐In the normal kidney sections, high‐energy adenine nucleotides (ATP and ADP) were significantly rich (vs. inner medulla) in both the cortex and the outer medulla (outer stripe of outer medulla [OSOM] and inner stripe of outer medulla [ISOM]). ‐ATP and total adenylates in the cortex and OSOM decreased by transient ischemia for 10 min: ‐ATP in the cortex and the outer medulla decreased within a minute after the clipping procedure, and adenosine, inosine, and hypoxanthine increased in every region of the kidney. In particular, the content of ATP decreased by 45% within a minute of ischemia, and the decrease reached 84% during 10 min ischemia. In the inner medulla, ATP did not decrease within a minute, and significant decline first became evident at 10 min after clipping. AMP increased in every region of the kidney during the ischemia. Energy charge value decreased in the whole kidney within a minute. Accumulation of adenosine in the OSOM disappeared after the clipping procedure, which was associated with the increase in adenosine in regions of the kidney except for the OSOM. ‐Inosine and hypoxanthine increased in every region of the kidney within a minute and in parallel to AMP, and the degrading changes in adenylates progressed during 10 min ischemia. Metabolome analysis revealed increase in xanthine and uric acid in the ischemic kidney. ‐In the reperfusion sections, restoration of ATP in the renal cortex and OSOM was not complete, and ATP showed a 24% decrease when compared with sham sections. In contrast, the restoration of ATP in the ISOM and inner medulla was sufficient. Total adenylates in the cortex and OSOM decreased after 24 h reperfusion, total adenylates were maintained in the ISOM and inner medulla: total adenylates and ATP in the cortex and OSOM after 24 h reperfusion demonstrated prolonged loss. The breakdown products of ATP were increased in the whole kidney by 10 min ischemia, almost recovered to the original content after 24 h reperfusion. A prolonged loss of ATP was significant after 10 min ischemia. ‐NADH showed a fivefold increase in all regions of the kidney subjected to 10 min ischemia. The increase in NADH in the cortex and OSOM persisted during 24 h of reperfusion, whereas it significantly decreased (vs. 10 min ischemia) in the ISOM and inner medulla.
Jouret et al. 2016 29	Mouse	The renal function was monitored by SCr and serum urea levels. IR‐exposed mice showed a significant increase in both AKI parameters. Note: no thresholds given.	SCr (increase post‐IR, recover 48 h post‐IR) Serum urea (increase post‐IR, recover 48 h post‐IR) Lactate (urinary and tissue levels increase post‐IR)	—	Urine: ‐Urine levels of taurine, lactate, and glucose were steadily increased after IR, urine levels of trimethylamine were significantly reduced. ‐Pathways significantly affected by renal IR: gluconeogenesis and taurine/hypotaurine metabolism at 6 and 24 h reperfusion. Protein biosynthesis, glycolysis, and galactose and arginine metabolisms appeared essential at 48 h reperfusion. Allantoin increased 24 h post‐IR, but decreased 48 h after. Tissue: ‐Similar discriminations in tissue: changes in levels of lactate, fatty acids, choline, and taurine. ‐The identification of metabolites, whose increased abundance reached significance in loading plots included fatty acids (and modified lipoproteins), lactate, and N‐acetyl groups of glycoproteins. ‐Levels of taurine and myo‐inositol were decreased in kidneys from IR mice in comparison to sham animals. ‐Analysis of metabolites at 6 h and 24 h reperfusion: taurine/hypotaurine and betaine metabolisms were significantly affected by renal IR. ‐At 48 h postreperfusion, IR‐associated cascades were protein biosynthesis, biotin, and taurine/hypotaurine metabolism. Serum: Serum analysis could not discriminate sham operated from IR‐exposed animals.
Legouis et al. 2020 3	Mouse	Not defined	SCr (increase post‐IR) BUN (increase post‐IR)	—	Mice exposed to severe IR injury displayed increased urea and creatinine levels, together with a decrease in glucose and increase in lactate serum levels at 48 h, whereas urinary glucose and lactate were unchanged except for one outlier. Blood lactate clearance was impaired in the IR group after intraperitoneal injection of sodium lactate. Increase in blood glucose following lactate injection was reduced in the IR group.
Poyan Mehr et al. 2018 30	Mouse	SCr was measured as a measure for renal function and postischemic injury. Note: no thresholds given.	SCr (increase post‐IR)	—	A total of 204 metabolites measured, 27 were more than twofold increased in postischemic urines compared to controls including several sugars and amino acids, a pattern consistent with tubular impairment. Among these metabolites was quinolinate, an intermediate in the de novo NAD+biosynthetic pathway from tryptophan. Many other metabolites, including amino acids and acyl‐carnitines, were differentially regulated in urine of AKI mice.
Rao et al. 2016 31	Mouse	Renal injury confirmed by SCr levels and histology. Note: no thresholds given.	SCr (increase post‐IR)	Histology	Only measured lipids: ‐Four lipids were changed (all increases) to a statistically significant extent at 6 h after IR. Of these, three were identified as ether‐linked phospholipids (one an abundant phosphatidylcholine (PC): PC O−38:1, and two PEs: an abundant PE O−42:3 and a minor PE O−40:4). The two abundant ether lipids were as follows: PC O−38:1 (PC O−18:0, 20:1) and PE O−42:3 (PE O−20:1, 22:2). PC O−38:1 is a plasmanylcholine, while PE O−42:3 is a plasmalogen. ‐Many more lipids were changed to a statistically significant extent at 24 h after IR. The abundant PC O−38:1 remained elevated in IR kidneys at 24 h compared with the 24‐h sham group, the low‐abundance PE O−40:4 was present at comparably low levels in kidneys of both IR and sham mice at 24 h. PE O−42:3 was present at high levels but was decreased at 24 h compared with its sham control group, this lipid was increased relative to its sham control group at 6 h post‐IR. All ether‐linked PEs and PEs detected 24 h post‐IR were reduced with AKI. ‐No statistically significant differences in major hydroxyoctadeca dienoic acids and hydroxyeicosatetra enoic acids or linoleic and arachidonic acids were detected in kidneys of sham and IR animals at 6 h post‐IR.
Wei et al. 2014 32	Mouse	Renal function: statistically significant differences in SCr or BUN levels compared to sham condition. Note: no thresholds given.	SCr (increase post‐IR, peak 48 h post‐IR, and recover 1 week post‐IR) BUN (increase post‐IR, peak 48 h post‐IR, and recover 1 week post‐IR) Lactate (tissue and serum levels decline post‐IR, but recover)	—	‐The changes started in renal cortex, followed by medulla and plasma. ‐Increased allantoin levels (specifically cortex, not medulla). ‐Elevated serum β‐hydroxybutyrate levels. ‐The kidney cortex and the plasma samples showed early decreases in glucose and lactate, but recovery to near‐sham levels by 1 week reperfusion time. ‐Some metabolites, such as 3‐indoxyl sulfate, were induced at the earliest time point of renal IR. ‐There was a notable switch of energy source from glucose to lipids. ‐Decreased polyols for osmotic regulation. ‐Several pathways involved in inflammation regulation were induced. ‐Late induction of prostaglandins.
Zager et al. 2014 33	Mouse	Severity of AKI was assessed by BUN and plasma creatinine concentrations and renal cortical NGAL mRNA levels. Note: no thresholds given	SCr (increase post‐IR) BUN (increase post‐IR)	—	Ischemia induced persistent pyruvate depletion. During ischemia, decreasing pyruvate levels correlated with increasing lactate levels. During early reperfusion, pyruvate levels remained depressed, but lactate levels fell below control levels. During late reperfusion, pyruvate depletion corresponded to increased gluconeogenesis (pyruvate consumption).
Pig
Clendenen et al. 2019 34	Pig	Not defined	Lactate (serum levels increase post‐IR) SCr (increase post‐IR)	—	‐Lactate increased in response to IR. Glutamate accumulation with a serum increase of 2.7 times from baseline occurring exclusively after reperfusion. Hypoxanthine increased 4 times baseline. IR changed arginine, proline, creatine, and polyamine metabolism. Arginine decreased. Proline increased 1.1 times baseline following IR. Creatinine with increased 1.6 times baseline. Arginine consumption and accumulation of ornithine and polyamines (putrescine, spermidine, and spermine) were observed upon IR. Spermine increased 5 times baseline levels, with spermidine following a similar trend. Putrescine increased. ‐Small molecule metabolites involved in redox homeostasis (e.g., reduced glutathione—GSH, cysteine, carnosine, kynurenine, taurine, and hypotaurine) and, in general, metabolites involved in glutathione turnover (5‐oxoproline) or sulfur metabolism (taurine, hypotaurine, methionine, and GSH) were affected. Taurine increased upon reperfusion. No substantial increases in the post‐IR circulating levels of carnitine, tryptophan, and serotonin.
Fonouni et al. 2011 35	Pig	Not defined	SCr (no “substantial” differences) BUN (no “substantial” differences) Lactate (extracellular fluid levels peak post‐IR, but recover to baseline)	—	Baseline (BL) value = measured parameters in donors at the beginning of the graft procurement. Baseline: Glucose 0.56 mM, lactate 0.46 mM, pyruvate 12.17 µM, glutamate 19.75 mM, and glycerol 19.58 µM Procurement: Glucose increase to 1.11 mM, lactate increase 0.54 mM, pyruvate increase 28.03 µM then decrease, glutamate increase to ~40 mM, and glycerol similar to BL CIT: Glucose decrease to 0.23 mM, lactate decrease until halfway then increase to 0.35 mM, pyruvate short increase to 20.02 µM then decrease to 4.85 µM, glutamate increase to 82.60 mM, and glycerol increase at end to 54.76 µM WIT: Glucose decrease 40 min to 0.14 mM then sharp increase to 0.48 mM, lactate increase to 0.75 mM, pyruvate increase to 10.18 µM, glutamate increase to 131 mM, and glycerol increase to 118.22 µM Reperfusion: Glucose increase 40 min 1.47 mM then decrease to 0.73 mM, lactate increase 20 min to 1.07 mM then decrease to 0.58 mM, pyruvate increase 40 min to 29.97 µM then decrease to 17.80 µM, glutamate increase 20 min to 161.60 mM then decrease 40 min to 41.03 mM and then steady, and glycerol increase 40 min to 236.70 µM then decrease to 19.60 µM
Hauet et al. 2000 36	Pig	Death: acute renal failure confirmed by histological analysis. These results were associated with prolonged oliguria or anuria. Assessment of renal function: creatinine clearance and fractional excretion of Na+demonstrated reduced renal function. Note: no thresholds given.	Creatinine clearance (decrease post‐IR, recover slightly)	Survival Urinary NAG excretion (increase post‐IR, recover slightly) Fractional Na+ excretion (increase post‐IR, recover to near‐baseline)	‐The urinary lactate/Cr ratio was significantly greater in the IR groups versus control. ‐Urinary citrate/Cr level was higher in control versus ischemia.
Malagrino et al. 2019 37	Pig	The animals showed changes characteristic of AKI: increased SCr, serum NGAL, fractional excretion of sodium, potassium, and chloride, and increased glucose and protein in urine. The most important result for the diagnosis of AKI was based on histological analysis, which showed acute tubular necrosis. An increase in nitrated protein in serum and urine was also observed. Note: no thresholds given.	SCr (increase post‐IR)	Histology Serum NGAL (increase post‐IR) Fractional Na+, K+, and Cl− excretion (increase post‐IR) Urinary glucose (increase post‐IR) Urinary protein (increase post‐IR)	Serum: ‐Metabolites that showed a quick increase or decrease after 60 min of ischemia, followed by a progressive return to baseline after reperfusion: L‐glutamate, L‐serine, N‐isovaleroylglycine, L‐methionine, L‐proline, 2‐aminobutyrate, and choline. These metabolites discriminate between the preischemic and ischemia periods, as well as between the ischemic and 11 h postreperfusion periods. However, as they returned to basal levels, they do not discriminate between the preischemia and reperfusion periods Urine: Focus on urinary metabolites increased immediately after the reperfusion (0.5 h postreperfusion), the result of “washing” the ischemic kidney. A sharp increase or decrease in 0.5 h postreperfusion period compared with the preischemia period: 3‐hydroxybutyrate, 3‐hydroxyisovalerate, methylguanidine, 3‐aminoisobutyrate, trigonelline, betaine, glycerol, trimethylamine, carnosine, citrate, N‐phenylacethylglycine, pyruvate, and 1‐methylnicotinamide. These metabolites were able to discriminate between the 0.5 h postreperfusion and preischemia periods. Pathway and network analysis: The metabolites identified were overrepresented in the canonical pathways of amino acids degradation, lipid metabolism, molecular transport, small molecule biochemistry, cell cycle, cellular assembly, and organization.
Dog
Maessen et al. 1989 38	Dog	Posttransplant viability	—	Survival	Energy metabolites measured: ATP, ADP, AMP, GTP, GDP, GMP, and IMP. CI with/without WI: −24 h CI: adenine nucleotide and guanine nucleotide contents decreased 30%. IMP increased. −48 h CI: no differences with 24 h CI. −30 min WI prior to CI: adenine and guanine nucleotide content already decreased before start of CI, increase in IMP. CI of 24 h after 30 min of WI did not affect content of adenine and guanine nucleotides, but IMP levels further increased. Prolonged CI to 48 h further decreased adenine and guanine nucleotide levels, while IMP did not show an additional increase. Reperfusion: 1 h of reperfusion after 24 or 48 h of CI resulted in increase in guanine nucleotide pool. The adenine nucleotides remained unaffected in the 24 h group, but dropped in the 48 h group. IMP levels were greatly reduced in both. When 30 min WI was applied prior to CI, some different patterns were observed. In WI groups, adenine nucleotide levels dropped in 24 h groups but remained unaffected in 48 h groups after 1 h reperfusion. The effect on guanine nucleotide and IMP levels did not differ from non‐WI groups. Following reperfusion, non‐WI groups showed higher (ATP+ADP)/AMP ratios.
Montañés et al. 1991 39	Dog	Not defined	Creatinine clearance (decrease post‐IR) BUN (increase post‐IR) Lactate (systemic serum levels similar post‐IR, kidney‐specific clearance decreased post‐IR)	—	Systemic blood: No significant changes in pH, bicarbonate, glutamine, glutamate, alanine, lactate, and pyruvate. Kidney specific (AV sampling): No significant changes in glutamine, glutamate, alanine, and pyruvate. Decreased lactate clearance. Renal cortex: Decreased glutamine, glutamate, ADP, AMP, and TAN. No significant changes in α‐ketoglutarate, aspartate, lactate, pyruvate, alanine, and ATP. Urine: Increased fractional excretion of lactate and pyruvate.

Results are (partially) quoted or paraphrased from the texts.

Abbreviations: AA, amino acid; AC, acylcarnitine; AV, arteriovenous; BUN, blood urea nitrogen; CA, cardiac arrest; CPB, cardiopulmonary bypass; CI, cold ischemia; CIT, cold ischemia time; dATP, deoxyadenosine triphosphate; DGF, delayed graft function; FA, fatty acid; fDGF, functional DGF; FFA, free fatty acid; IR, ischemia reperfusion; ISOM, inner stripe of outer medulla; KIM‐1, kidney injury molecule‐1; NAG, N‐acetyl‐β‐D‐glucosaminidase; NGAL, neutrophil gelatinase‐associated lipocalin; OSOM, outer stripe of outer medulla; PC, phosphatidylcholine; PE, phosphatidylethanolamine; Post‐I, postischemia; Pre‐I, preischemia; PUFA, poly unsaturated fatty acids; SCr, serum creatinine; TAN, total adenine nucleotides; TMAO, trimethylamine oxide; WI, warm ischemia; WIT, warm ischemia time.

^a Additionally included study.