Manipulation of lipid metabolism during normothermic machine perfusion: Effect of defatting therapies on donor liver functional recovery

BACKGROUND Strategies to increase steatotic donor livers' utilisation are required to tackle the mortality on the transplant waiting list. We aimed to test the efficacy of pharmacological enhancement of the lipid metabolism of human livers during ex-situ normothermic machine perfusion to promote defatting and improve the functional recovery of the organs. METHODS Ten livers discarded because of steatosis were allocated to a defatting group that had the perfusate supplemented with a combination of drugs to enhance lipid metabolism or a control group that received perfusion fluid with vehicle only. Steatosis was assessed using tissue homogenate and histological analysis. Markers for lipid oxidation and solubilisation, oxidative injury, inflammation and biliary function were evaluated by ELISA, immunohistochemistry and in-gel protein detection. RESULTS Treatment reduced tissue triglycerides by 38% and macrovesicular steatosis by 40% over 6 hours. This effect was driven by increased solubilisation of triglycerides (p=0.04); and mitochondrial oxidation as assessed by increased ketogenesis (p=0.008) and adenosine triphosphate synthesis (p=0.01) associated with raised levels of the enzymes ACOX-1, CPT1A and acetyl-CoA synthetase. Concomitantly, defatted livers exhibited enhanced metabolic functional parameters such as urea production (p=0.03), lower vascular resistance, lower release of alanine aminotransferase (p=0.049) and higher bile production (p=0.008) with a higher bile pH (p=0.03). The treatment downregulated the expression of markers for oxidative injury, activation of immune cells (CD-14; CD-11b) and reduced the release of inflammatory cytokines in the perfusate (TNF-α; IL-1β). CONCLUSION Pharmacological enhancement of intracellular lipid metabolism during normothermic machine perfusion decreased the lipid content of human livers within 6 hours. It also improved the intracellular metabolic support to the organs leading to successful functional recovery and decreased expression of markers of reperfusion injury. This article is protected by copyright. All rights reserved.