Defatting of donor transplant livers during normothermic perfusion-a randomised clinical trial: study protocol for the DeFat study

Abstract

Background: Liver disease is the third leading cause of premature death in the UK. Transplantation is the only successful treatment for end-stage liver disease but is limited by a shortage of suitable donor organs. As a result, up to 20% of patients on liver transplant waiting lists die before receiving a transplant. A third of donated livers are not suitable for transplant, often due to steatosis. Hepatic steatosis, which affects 33% of the UK population, is strongly associated with obesity, an increasing problem in the potential donor pool. We have recently tested defatting interventions during normothermic machine perfusion (NMP) in discarded steatotic human livers that were not transplanted. A combination of therapies including forskolin (NKH477) and L-carnitine to defat liver cells and lipoprotein apheresis filtration were investigated. These interventions resulted in functional improvement during perfusion and reduced the intrahepatocellular triglyceride (IHTG) content. We hypothesise that defatting during NMP will allow more steatotic livers to be transplanted with improved outcomes.

Methods: In the proposed multi-centre clinical trial, we will randomly assign 60 livers from donors with a high-risk of hepatic steatosis to either NMP alone or NMP with defatting interventions. We aim to test the safety and feasibility of the defatting intervention and will explore efficacy by comparing ex-situ and post-reperfusion liver function between the groups. The primary endpoint will be the proportion of livers that achieve predefined functional criteria during perfusion which indicate potential suitability for transplantation. These criteria reflect hepatic metabolism and injury and include lactate clearance, perfusate pH, glucose metabolism, bile composition, vascular flows and transaminase levels. Clinical secondary endpoints will include proportion of livers transplanted in the two arms, graft function; cell-free DNA (cfDNA) at follow-up visits; patient and graft survival; hospital and ITU stay; evidence of ischemia-reperfusion injury (IRI); non-anastomotic biliary strictures and recurrence of steatosis (determined on MRI at 6 months).

Discussion: This study explores ex-situ pharmacological optimisation of steatotic donor livers during NMP. If the intervention proves effective, it will allow the safe transplantation of livers that are currently very likely to be discarded, thereby reducing waiting list deaths.

Trial registration: ISRCTN ISRCTN14957538. Registered in October 2022.

Keywords: Defatting; Functional assessment; Hepatic steatosis; Liver transplantation; Non-alcoholic fatty liver disease (NAFLD); Normothermic machine perfusion (NMP).

Fig. 1

A–B Comparison of circulating TG (A) and 3-OHB (B) in the perfusate during NMP between steatotic (n = 18) and lean (n = 15) livers. Data presented as mean ± SD. *p < 0.05, **p < 0.01

Fig. 2

Overview of hepatic fatty acid (FA) input, synthesis and disposal in the postprandial state. FA input to the liver derives from 1) the lipolysis of adipose (subcutaneous and visceral) tissue triglyceride (TG), and 2) dietary fat, which enter the liver as either chylomicron remnants or chylomicron-derived spillover FAs. 3) FA synthesis occurs within the liver, via de novo lipogenesis (DNL) which involves the synthesis of FA from acetyl-CoA derived from non-lipid precursors, such as glucose. FAs enter a common pool and are broadly partitioning between two pathways for disposal: 4) the esterification pathway, where predominantly TG is produced which can then be either stored in the cytosol (as a lipid droplet) or can lipidate very-low density lipoprotein (VLDL) in the endoplasmic reticulum (ER) to form VLDL-TG and then secreted into the systemic circulation, or 5) oxidation either via the tricarboxylic acid (TCA) cycle to form CO2, or the ketogenic pathway where β-hydroxybutyrate (3OHB) is produced and enters the systemic circulation

Fig. 3

Lipoprotein apheresis filter in NMP circuit

Fig. 4

A–D Group 1 NMP alone, Group 2 filter and Group 3 filter plus defatting agents

Fig. 5

Eligibility screening of donor livers and eligible participants for the DeFat study. *Consent refers to evidence of a signed informed consent form. If a patient on the waiting list has indicated intention to consent and has not returned the signed consent form prior to admission for transplant, they will be asked to sign and confirm consent on admission for transplant. Randomisation and perfusion will only be carried out if the informed consent form has been signed

Fig. 6

Flow of participants through the study. NMP normothermic machine perfusion, MRCP magnetic resonance cholangiopancreatography, ALT alanine transaminase