Table 4.

Metabolomics in liver preservation for Tx.

Authors	Model	Metabolomics	Results
Animal studies
Busza et al., 1994 [54]	SCS (48 h) in plasma-like vs. modified UW followed by 1 h HMP; Rats DBD without Tx; N = 10	31P NMR spectroscopy; Metabolites from whole organ	After 48 h of SCS: ↓ ATP, ↓ ADP, ↑ inorganic phosphate; Plasma-like vs. modified UW solution (after reperfusion) Modified UW: ↑ β-ATP/NAD(H) ratio, ↓ inorganic phosphate
Changani et al., 1996 [55]	SCS (4 h) followed by 2 h oxygenated HMP; Porcine DBD without Tx; N = 5	31P NMR spectroscopy; Metabolites from tissue	During 4 h SCS: ↓ nucleotide triphosphates, ↑ 3-phosphoglycerate, ↑ 2,3 diphosphoglycerate, ~glycerophosphorylcholine, ~glycerophosphorylethanolamine; After 2 h of oxygenated HMP: ↑ nucleotide triphosphates, ↓ 3-phosphoglycerate, ↓ 2,3 diphosphoglycerate, ↓ glycerophosphorylcholine, ↓ glycerophosphorylethanolamine
Changani et al., 1997 [56]	SCS (2 vs. 24 h) followed by 2 h oxygenated HMP; Porcine DBD without Tx; N = 6	31P NMR spectroscopy; Metabolites from perfusate	2 vs. 24 h of SCS followed by 20 min oxygenated HMP 24 h: ↓ β-ATP, ↓ α-ATP; ↓ β-ATP, ↓ phosphomonoesters, ~inorganic phosphate, ↓ phosphodiesters, ↓ methylene diphosphonic acid; 2 vs. 24 h of SCS during 2 h oxygenated HMP 24 h: ↓ ATP
Gibelin et al., 2000 [57]	SCS in EC vs. UW solution (24 h) followed by 90 min reperfusion; Rat DBD without Tx; N = 10	NMR spectroscopy; Metabolites from perfusate	SCS in EC vs. UW UW: ↑ lactates, ↑ pyruvate, ↑ succinate, ↑ citrate, ↑ aceto-acetate, ↑ β-hydroxybutyrate
Habib et al., 2004 [58]	SCS (40 min) followed by 6 h NMP; Rabbits DBD vs. DCD without Tx; N = 4/group	1H NMR spectroscopy; Metabolites from bile	During 6 h NMP: ↑ bile acids, ↑ lactate, ↑ glucose, ↑ phosphatidylcholine, ↓ acetate; DBD vs. DCD DBD: ↓ bile acids, ↓ lactate, ↓ glucose, ↓ phosphatidylcholine, ↑ acetate
Liu et al., 2009 [59]	HMP (4 h); Porcine DCD (WI 4 h) vs. DBD without Tx; N = 11	1H NMR spectroscopy; Metabolites from perfusate	During HMP: ↑ lactate, ↑ alanine, ↑ histidine; DCD vs. DBD DCD: ↑ alanine, ↑ histidine
Fontes et al., 2015 [60]	SNMP with HBOC vs. SCS (9 h); Porcine DBD with Tx; N = 12	GC-MS; Over 600 metabolites from perfusate and bile	SNMP vs. SCS SNMP in perfusate: ↑ ascorbate, ↑ threonate, ↓ AMP, ↓ hypoxanthine, ↑ glucose, ↑ BCAA (valine, isoleucine and leucine), ↓ 12-hydroxyeicosatetraenoic acid; SNMP in bile: ↓ taurocholate, ↓ glycochenodeoxycholate, ↓ taurine, ↓ hypotaurine, ↑ lathosterol, ↑ campesterol, ↓ α-hydroxybutyrate, ↓ glycocholenate sulfate
Human studies
Lanir et al., 1988 [61]	SCS (1.9–6.8 h); DBD and DCD with Tx; N = 25	LC-MS; Metabolites from tissue	Prior to Tx Success: ↑ ATP, ↑ ADP, ~AMP, ↑ ATP/ADP ratio, ↑ energy change, ↑ total adenine nucleotide content, ↑ guanosine diphosphate, ↑ uridine triphosphate, ~hypoxanthine, ~xanthine, ~NAD +
Duarte et al., 2005 [62]	SCS (9–13 h) DBD with Tx; N = 6	1H NMR spectroscopy; Metabolites from tissue	Before retrieval vs. after SCS vs. post Tx PGF: ↑ glycerophosphocholine; PGD: ~glycerophosphocholine; Steatotic vs. non-steatotic grafts Steatotic: ↑ triglycerides, ↓ phospholipids, ↓ amino acids, ↓ glucose, ↓ nucleotide-related compounds, ↓ clearance of UW
Bruinsma et al., 2016 [63]	SNMP (3 h); DCD vs. ECD without Tx; N = 21	LC-MS and GC-MS; 159 metabolites from perfusate and tissue	0 vs. 3 h of SNMP: ↓ carbohydrates (glucose-6-phosphate, fructose-6-phosphate, glycerol, xylitol, ribulose-5-phosphate, N-acetylmannosamine, maltose, raffinose, glyceric acid), ↑ amino acids (valine, threonine, proline, leucine, isoleucine and glutamine), ↑ citric acid, ↑ α-ketoglutarate, ↓ lactic acid, ↑ 2-hydroxyglutaric acid, ↑ urea, ↓ uric acid, ↑ oxoproline, ↓ N-acetyl-D-hexosamine; 0→3 h of SNMP: ↑ amino acids (valine, threonine, leucine and isoleucin), ↓ lactic acid; DCD vs. ECD DCD: ↑ ATP, ↓ oxidized glutathione/glutathione ratio, ↓ NADH/NAD ratio
Karimian et al., 2019 [64]	SNMP vs. NMP (3 h); DBD/DCD (steatosis >30%) without Tx; N = 14;	LC-MS; Over 1600 metabolites from tissue	After 3 h of SNMP vs. NMP SNMP: ↓ glutathione, ↓ cysteinylglycine, ↑ 5-oxoproline, ↑ glutamate, ↓ cysteine, ↑ glycine, ↓ γ-glutamylcysteine, ↑ citrate, ↓ α-ketoglutarate, ↓ succinate, ↑ fumarate, ↑ malate, ↓ maltopentaose, ↓ maltotriose, ↓ maltose
Raigani et al., 2020 [65]	NMP (3 h); DBD/DCD (non-steatotic vs. steatotic) without Tx; N = 8;	LC-MS; Over 1600 metabolites from tissue	Non-steatotic vs. steatotic after 3 h of NMP Non-steatotic: ↑ glutathione, ↓ oxidized glutathione, ↑ N-acetylcysteine, ~ATP/ADP ratio, ↑ carnitine, ↓ β-hydroxybutyrate, ~citrate, ↓ α-ketoglutarate, ↑ succinate, ↑ fumarate, ↑ malate, ↑ glucose-6-phosphate, ~dihydroxyacetone phosphate, ↑ 2-phosphoglycerate, ↑ phosphoenolpyruvate, ↑ ribulose-5-phosphate, ↑ ribose-5-phosphate, ↑ xylulose-5-phosphate, ↑ eicosapentaenoic acid, ↑ docosapentaenoic acid, ↑ docosahexaenoic acid, ↑ cholesterol, ~taurine, ~choline
Xu et al., 2020 [66]	SCS (210–840 min); DBD vs. DCD with Tx; N = 47	LC-MS; Metabolites from tissue	DBD vs. DCD DBD: ↑ AMP/urate ratio, ↑ adenosine/urate ratio, ↑ adenine/urate ratio, ↑ hypoxanthine/urate ratio; EGF vs. EAD EGF: ↑ AMP/urate ratio, ~adenosine/urate ratio, ↑ adenine/urate ratio, ~hypoxanthine/urate ratio

ADP, adenosine diphosphate; AMP, adenosine monophosphate; ATP, adenosine triphosphate; BCAA, branched-chain amino acid; DBD, donation after brain death; DCD, donation after circulatory death; EC, Euro-Collins solution; ECD, extended criteria donor; EAD, early allograft dysfunction; EGF, early graft function; GC-MS, gas chromatography–mass spectrometry; HBOC, hemoglobin-based oxygen carrier; HMP, hypothermic machine perfusion; LC-MS, liquid chromatography–mass spectrometry; NADH, nicotinamide adenine dinucleotide; NMP, normothermic machine perfusion; NMR, nuclear magnetic resonance; PGD, primary graft dysfunction; PGF, primary graft function; SCS, static cold storage; SNMP, subnormothermic machine perfusion; Tx, transplantation; UW, University of Wisconsin solution; WI, warm ischemia time.