Introduction: Liver is the major site for nitrogen metabolism. Most hepatic transcriptional activity is related to protein-specific synthesis. Liver preservation has a direct impact in AA anabolic and catabolic pathways and post-reperfusion events. This study aimed to compare the AA metabolic pathways experienced by porcine liver allografts submitted to two different methods of organ preservation. Methods: Swine liver allografts preserved by MP combined with a hemoglobin-based oxygen carrier (HBOC) at 21[deg]C (n=6) were compared to livers undergoing CS (n=6) over a 9 hour period. Both groups had tissue and perfusate samples obtained before, during and after preservation. Tissue samples were submitted to histology, transcriptomics, proteomics, and metabolomics analyses. Albumin serum levels were followed post-operatively. Results: AA synthesis increased during MP (vs. CS group) as evident by increased tissue levels of non-essential AAs: alanine (p=0.02), glutamate (p=0.007), serine (p=0.008), glycine (p=0.01), and glutamine (p=0.045). In addition, tissue levels of essential amino acids significantly increased suggesting degradation of un-necessary large proteins during MP: lysine (p<0.001), leucine (p=0.005), tryptophan (p=0.022), valine (p=0.004), and phenylalanine (p=0.008). In the MP group, expression ratios of genes involved in collagen synthesis were kept near 90% and five genes were upregulated: procollagen C-endopeptidase and Type VII collagen. Genes involved in synthesis of major proteins were mildly upregulated: albumin, transthyretin, transferrin, ceruloplasmin, plasminogen activator and coagulation factor III. Expression of lipoprotein-related genes was mildly downregulated and HDL binding protein and apolipoproteins were mildly upregulated in the MP group. In addition, higher levels of 2-aminoadipate (p=0.01) in the CS group suggested higher oxidative stress in cold preserved livers. Albumin serum levels were significantly (p<0.05) higher in the MP group post-operatively. The MP group had a significantly higher survival (100%) when compared to the CS group (33%). Conclusion: MP with HBOC at 21[deg]C sustains active protein-coding gene expression in liver allografts during preservation. The AA metabolic pathways at 21[deg]C, are mainly characterized by deamination and transamination, synthesis of non-essential AAs, Glucogenic AAs, urea, major plasma proteins, collagen and clotting factors. CS induces higher oxidative stress and subsequent AA catabolism.

CITATION INFORMATION: Banan B, Lopez R, Hughes C, Michalopoulos G, Fontes P. Amino Acid (AA) Metabolism During Liver Allograft Preservation Comparing Subnormothermic Machine Perfusion (MP) Against Cold Storage (CS). Am J Transplant. 2016;16 (suppl 3).

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