LDHB contributes to the regulation of lactate levels and basal insulin secretion in human pancreatic ß cells.

Using 13C6 glucose labeling coupled to gas chromatography-mass spectrometry and 2D 1H-13C heteronuclear single quantum coherence NMR spectroscopy, we have obtained a comparative high-resolution map of glucose fate underpinning ß cell function. In both mouse and human islets, the contribution of glucose to the tricarboxylic acid (TCA) cycle is similar. Pyruvate fueling of the TCA cycle is primarily mediated by the activity of pyruvate dehydrogenase, with lower flux through pyruvate carboxylase. While the conversion of pyruvate to lactate by lactate dehydrogenase (LDH) can be detected in islets of both species, lactate accumulation is 6-fold higher in human islets. Human islets express LDH, with low-moderate LDHA expression and ß cell-specific LDHB expression. LDHB inhibition amplifies LDHA-dependent lactate generation in mouse and human ß cells and increases basal insulin release. Lastly, cis-instrument Mendelian randomization shows that low LDHB expression levels correlate with elevated fasting insulin in humans. Thus, LDHB limits lactate generation in ß cells to maintain appropriate insulin release.

The Current Role and Future Applications of Machine Perfusion in Liver Transplantation.

The relative paucity of donor livers suitable for transplantation has sparked innovations to preserve and recondition organs to expand the pool of transplantable organs. Currently, machine perfusion techniques have led to the improvement of the quality of marginal livers and to prolonged cold ischemia time and have allowed for the prediction of graft function through the analysis of the organ during perfusion, improving the rate of organ use. In the future, the implementation of organ modulation might expand the scope of machine perfusion beyond its current usage. The aim of this review was to provide an overview of the current clinical use of machine perfusion devices in liver transplantation and to provide a perspective for future clinical use, including therapeutic interventions in perfused donor liver grafts.

Predicting Early Allograft Function After Normothermic Machine Perfusion.

BACKGROUND: Normothermic ex situ liver perfusion is increasingly used to assess donor livers, but there remains a paucity of evidence regarding criteria upon which to base a viability assessment or criteria predicting early allograft function. METHODS: Perfusate variables from livers undergoing normothermic ex situ liver perfusion were analyzed to see which best predicted the Model for Early Allograft Function score. RESULTS: One hundred fifty-four of 203 perfused livers were transplanted following our previously defined criteria. These comprised 84/123 donation after circulatory death livers and 70/80 donation after brain death livers. Multivariable analysis suggested that 2-h alanine transaminase, 2-h lactate, 11 to 29 mmol supplementary bicarbonate in the first 4 h, and peak bile pH were associated with early allograft function as defined by the Model for Early Allograft Function score. Nonanastomotic biliary strictures occurred in 11% of transplants, predominantly affected first- and second-order ducts, despite selection based on bile glucose and pH. CONCLUSIONS: This work confirms the importance of perfusate alanine transaminase and lactate at 2-h, as well as the amount of supplementary bicarbonate required to keep the perfusate pH > 7.2, in the assessment of livers undergoing perfusion. It cautions against the use of lactate as a sole indicator of viability and also suggests a role for cholangiocyte function markers in predicting early allograft function.

Systematic review, meta-analysis and single-centre experience of the diagnostic accuracy of intraoperative near-infrared indocyanine green-fluorescence in detecting pancreatic tumours.

BACKGROUND: During pancreatic resections assessing tumour boundaries and identifying the ideal resection margins can be challenging due to the associated pancreatic gland inflammation and texture. This is particularly true in the context of minimally invasive surgery, where there is a very limited or absent tactile feedback. Indocyanine green (ICG) fluorescence imaging can assist surgeons by simply providing valuable real-time intraoperative information at low cost with minimal side effects. This meta-analysis summarises the available evidence on the use of near-infrared fluorescence imaging with ICG for the intraoperative visualization of pancreatic tumours (PROSPERO ID: CRD42021247203). METHODS: MEDLINE, Embase, and Web Of Science electronic databases were searched to identify manuscripts where ICG was intravenously administered prior to or during pancreatic surgery and reporting the prevalence of pancreatic lesions visualised through fluorescence imaging. RESULTS: Six studies with 7 series' reporting data on 64 pancreatic lesions were included in the analysis. MINOR scores ranged from 6 to 10, with a median of 8. The most frequent indications were pancreatic adenocarcinoma and neuroendocrine tumours. In most cases (67.2%) ICG was administered during surgery. ICG fluorescence identified 48/64 lesions (75%) with 81.3% accuracy, 0.788 (95%CI 0.361-0.961) sensitivity, 1 (95%CI 0.072-1) specificity and positive predictive value of 0.982 (95%CI 0.532-1). In line with the literature, ICG fluorescence identified 5/6 (83.3%) of pancreatic lesions during robotic pancreatic resections performed at our Institution. CONCLUSION: This meta-analysis is the first summarising the results of ICG immunofluorescence in detecting pancreatic tumours during surgery, showing good accuracy. Additional research is needed to define optimal ICG administration strategies and fluorescence intensity cut-offs.

Machine perfusion of the liver: applications in transplantation and beyond.

The shortage of donor livers considered suitable for transplantation has driven the development of novel methods for organ preservation and reconditioning. Machine perfusion techniques can improve the quality of marginal livers, extend the time for which they can be preserved and enable an objective assessment of their quality and viability. These benefits can help avoid the needless wastage of organs based on hypothetical concerns regarding quality. As machine perfusion techniques are gaining traction in clinical practice, attention has now shifted to their potential applications beyond transplantation. As well as providing an update on the current status of machine perfusion in clinical practice, this Perspective discusses how this technology is being used as a tool for therapeutic interventions including defatting of steatotic livers, immunomodulation and gene therapies.

Noninvasive assessment of steatosis and viability of cold-stored human liver grafts by MRI.

PURPOSE: A shortage of suitable donor livers is driving increased use of higher risk livers for transplantation. However, current biomarkers are not sensitive and specific enough to predict posttransplant liver function. This is limiting the expansion of the donor pool. Therefore, better noninvasive tests are required to determine which livers will function following implantation and hence can be safely transplanted. This study assesses the temperature sensitivity of proton density fat fraction and relaxometry parameters and examines their potential for assessment of liver function ex vivo. METHODS: Six ex vivo human livers were scanned during static cold storage following normothermic machine perfusion. Proton density fat fraction, T1 , T2 , and T2∗ were measured repeatedly during cooling on ice. Temperature corrections were derived from these measurements for the parameters that showed significant variation with temperature. RESULTS: Strong linear temperature sensitivities were observed for proton density fat fraction (R2 = 0.61, P < .001) and T1 (R2 = 0.78, P < .001). Temperature correction according to a linear model reduced the coefficient of repeatability in these measurements by 41% and 36%, respectively. No temperature dependence was observed in T2 or T2∗ measurements. Comparing livers deemed functional and nonfunctional during normothermic machine perfusion by hemodynamic and biochemical criteria, T1 differed significantly: 516 ± 50 ms for functional versus 679 ± 60 ms for nonfunctional, P = .02. CONCLUSION: Temperature correction is essential for robust measurement of proton density fat fraction and T1 in cold-stored human livers. These parameters may provide a noninvasive measure of viability for transplantation.

Urine Recirculation Improves Hemodynamics and Enhances Function in Normothermic Kidney Perfusion.

The study compares urine recirculation (URC) to urine replacement (UR) with Ringer's lactate in a porcine normothermic kidney machine perfusion (NMP) model using a preclinical prototype device. METHODS: Kidney pairs were recovered uninjured (as live-donor nephrectomy) and perfused consecutively. Pig kidneys (n = 10) were allocated to either NMP with URC (n = 5) or NMP with volume replacement (n = 5). Cold ischemia time was either 2 or 27 hours for the first or second perfusion (URC or UR) of a kidney pair. An autologous blood-based perfusate, leukocyte-filtered, was used and NMP performed up to 24 hours. Perfusion parameters, biochemistry/metabolic parameters were monitored and samples collected. RESULTS: Physiological mean arterial pressures and flows were achieved in both groups but were sustainable only with URC. Significantly higher arterial flow was observed with URC (326.7 ± 1.8 versus 242.5 ± 14.3 mL/min, P = 0.001). Perfusate sodium levels were lower with URC, 129.6 ± 0.7 versus 170.3±2.7 mmol/L, P < 0.001). Stable physiological pH levels were only observed with URC. Perfusate lactate levels were lower with URC (2.2 ± 0.1 versus 7.2 ± 0.5 mmol/L, P < 0.001). Furthermore, the hourly rate of urine output was lower with URC and closer to physiological levels (150 versus 548 mL/h, P = 0.008). Normothermic kidney perfusion with URC was associated with longer achievable durations of perfusion: the objective in all experiments was a 24-hour perfusion, but this was not achieved in every case. The mean perfusions were 17.3 ± 9.2 hours with URC versus 5.3 ± 1.3 hours NMP with UR; P = 0.02. There appeared to be no differences in baseline tubular condition with and without URC. CONCLUSIONS: URC facilitates long-term kidney NMP in a porcine model. Perfusate homeostasis and stability of renal arterial flow throughout the perfusion period was only achievable with URC, independent of cold ischemia time duration.

Transient Cold Storage Prior to Normothermic Liver Perfusion May Facilitate Adoption of a Novel Technology.

Clinical adoption of normothermic machine perfusion (NMP) may be facilitated by simplifying logistics and reducing costs. This can be achieved by cold storage of livers for transportation to recipient centers before commencing NMP. The purpose of this study was to assess the safety and feasibility of post-static cold storage normothermic machine perfusion (pSCS-NMP) in liver transplantation. In this multicenter prospective study, 31 livers were transplanted. The primary endpoint was 30-day graft survival. Secondary endpoints included the following: peak posttransplant aspartate aminotransferase (AST), early allograft dysfunction (EAD), postreperfusion syndrome (PRS), adverse events, critical care and hospital stay, biliary complications, and 12-month graft survival. The 30-day graft survival rate was 94%. Livers were preserved for a total of 14 hours 10 minutes ± 4 hours 46 minutes, which included 6 hours 1 minute ± 1 hour 19 minutes of static cold storage before 8 hours 24 minutes ± 4 hours 4 minutes of NMP. Median peak serum AST in the first 7 days postoperatively was 457 U/L (92-8669 U/L), and 4 (13%) patients developed EAD. PRS was observed in 3 (10%) livers. The median duration of initial critical care stay was 3 days (1-20 days), and median hospital stay was 13 days (7-31 days). There were 7 (23%) patients who developed complications of grade 3b severity or above, and 2 (6%) patients developed biliary complications: 1 bile leak and 1 anastomotic stricture with no cases of ischemic cholangiopathy. The 12-month overall graft survival rate (including death with a functioning graft) was 84%. In conclusion, this study demonstrates that pSCS-NMP was feasible and safe, which may facilitate clinical adoption.

A Back-to-Base Experience of Human Normothermic Ex Situ Liver Perfusion: Does the Chill Kill?

Normothermic machine perfusion (NMP) has been shown to protect livers from injury between procurement and transplantation in a randomized controlled trial, where the machine was transported to and from the donor center. The aim of this study was to determine whether an alternative, more practical back-to-base approach after initial static cold storage would compromise beneficial outcomes. Between February 2015 and June 2018, a nonrandomized pilot study was performed at a single site. Outcomes of back-to-base livers (n = 26) were compared with those of grafts procured locally that underwent immediate NMP (n = 17). The primary outcome measure (safety) was defined as 30-day patient and graft survival. A total of 46 liver grafts were perfused with NMP, of which 3 were discarded based on poor ex situ perfusion function. The 30-day patient and graft survival in the back-to-base and local NMP groups were both 100% (primary outcome: safety). Despite significantly prolonged mean cold ischemia time (6 versus 3.2 hours; P = 0.001), the back-to-base livers demonstrated no difference in graft function, incidence of complications, or graft and patient survival. In conclusion, the back-to-base approach was safe, did not compromise the overall benefit of NMP, and offers a practical alternative to portable normothermic ex situ machine transport.

The future of organ perfusion and re-conditioning.

Organ preservation and re-conditioning using machine perfusion technologies continue to generate promising results in terms of viability assessment, organ utilization and improved initial graft function. Here, we summarize the latest findings and study the results of ex-vivo/ex-situ hypothermic (HMP) and normothermic machine perfusion (NMP) in the area of abdominal organ transplantation (kidney, liver, pancreas and intestine). We also consider the potential role of normothermic regional perfusion (NRP) to re-condition donors after circulatory death organs before retrieval. The findings from clinical studies reported to date suggest that machine perfusion will offer real benefits when compared with conventional cold preservation. Several randomized trials are expected to report their findings within the next 2 years which may shed light on the relative merits of different perfusion methods and could indicate which perfusion parameters may be most useful to predict organ quality and viability. Further work is needed to identify composite endpoints that are relevant for transplanted organs that have undergone machine preservation. Multi-centre trials to compare and analyse the combinations of NRP followed by HMP and/or NMP, either directly after organ retrieval using transportable devices or when back-to-base, are needed. The potential applications of machine preservation technology beyond the field of solid organ transplantation are also considered.

Studying non-alcoholic fatty liver disease: the ins and outs of in vivo, ex vivo and in vitro human models.

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing. Determining the pathogenesis and pathophysiology of human NAFLD will allow for evidence-based prevention strategies, and more targeted mechanistic investigations. Various in vivo, ex situ and in vitro models may be utilised to study NAFLD; but all come with their own specific caveats. Here, we review the human-based models and discuss their advantages and limitations in regards to studying the development and progression of NAFLD. Overall, in vivo whole-body human studies are advantageous in that they allow for investigation within the physiological setting, however, limited accessibility to the liver makes direct investigations challenging. Non-invasive imaging techniques are able to somewhat overcome this challenge, whilst the use of stable-isotope tracers enables mechanistic insight to be obtained. Recent technological advances (i.e. normothermic machine perfusion) have opened new opportunities to investigate whole-organ metabolism, thus ex situ livers can be investigated directly. Therefore, investigations that cannot be performed in vivo in humans have the potential to be undertaken. In vitro models offer the ability to perform investigations at a cellular level, aiding in elucidating the molecular mechanisms of NAFLD. However, a number of current models do not closely resemble the human condition and work is ongoing to optimise culturing parameters in order to recapitulate this. In summary, no single model currently provides insight into the development, pathophysiology and progression across the NAFLD spectrum, each experimental model has limitations, which need to be taken into consideration to ensure appropriate conclusions and extrapolation of findings are made.

A randomized trial of normothermic preservation in liver transplantation.

Liver transplantation is a highly successful treatment, but is severely limited by the shortage in donor organs. However, many potential donor organs cannot be used; this is because sub-optimal livers do not tolerate conventional cold storage and there is no reliable way to assess organ viability preoperatively. Normothermic machine perfusion maintains the liver in a physiological state, avoids cooling and allows recovery and functional testing. Here we show that, in a randomized trial with 220 liver transplantations, compared to conventional static cold storage, normothermic preservation is associated with a 50% lower level of graft injury, measured by hepatocellular enzyme release, despite a 50% lower rate of organ discard and a 54% longer mean preservation time. There was no significant difference in bile duct complications, graft survival or survival of the patient. If translated to clinical practice, these results would have a major impact on liver transplant outcomes and waiting list mortality.

Normothermic Machine Preservation of the Liver: State of the Art.

PURPOSE OF REVIEW: This review aims to introduce the concept of normothermic machine perfusion (NMP) and its role in liver transplantation. By discussing results from recent clinical studies and highlighting the potential opportunities provided by this technology, we aim to provide a greater insight into NMP and the role it can play to enhance liver transplantation. RECENT FINDINGS: NMP has recently been shown to be both safe and feasible in liver transplantation and has also demonstrated its superiority to traditional cold storage in terms of early biochemical liver function. Through the ability to perform a viability assessment during preservation and extend preservation times, it is likely that an increase in organ utilisation will follow. NMP may facilitate the enhanced preservation with improved outcomes from donors after cardiac death and steatotic livers. Furthermore, it provides the exciting potential for liver-directed therapeutic interventions. SUMMARY: Evidence to date suggests that NMP facilitates the enhanced preservation of liver grafts with improved early post-transplant outcomes. The key role for this technology is to increase the number and quality of liver grafts available for transplantation and to reduce waiting list deaths.

The case for normothermic machine perfusion in liver transplantation.

In recent years, there has been growing interest in normothermic machine perfusion (NMP) as a preservation method in liver transplantation. In most countries, because of a donor organ shortage, an unacceptable number of patients die while awaiting transplantation. In an attempt to increase the number of donor organs available, transplant teams are implanting a greater number of high-risk livers, including those from donation after circulatory death, older donors, and donors with steatosis. NMP maintains the liver ex vivo on a circuit by providing oxygen and nutrition at 37°C. This permits extended preservation times, the ability to perform liver viability assessment, and the potential for liver-directed therapeutic interventions during preservation. It is hoped that this technology may facilitate the enhanced preservation of marginal livers with improved posttransplant outcomes by reducing ischemia/reperfusion injury. Clinical trials have demonstrated its short-term superiority over cold storage in terms of early biochemical liver function, and it is anticipated that it may result in increased organ utilization, helping to reduce the number of wait-list deaths. However, further studies are required to demonstrate longer-term efficacy and the impact on biliary complications as well as further knowledge to exploit and maximize the potential of this exciting new technology. Liver Transplantation 24 269-275 2018 AASLD.

Cold storage or normothermic perfusion for liver transplantation: probable application and indications.

PURPOSE OF REVIEW: Preservation of the liver via normothermic machine perfusion (NMP) is rapidly becoming an area of great academic and clinical interest. This review focuses on the benefits and limitations of NMP and where the role for static cold storage may lie. RECENT FINDINGS: Clinical studies have recently been published reporting the use of NMP in liver preservation for transplantation. They have described the technology to be well tolerated and feasible with potentially improved posttransplant outcomes. NMP facilitates extended preservation times as well as the potential to increase organ utilization through viability assessment and regeneration. However, this technology is considerably more costly than cold storage and carries significant logistical challenges. Cold storage remains the gold standard preservation for standard criteria livers with good long-term patient and graft survival. SUMMARY: NMP is an exciting new technological advancement in liver preservation, which is likely to have a positive impact in liver transplantation. However, randomized controlled trials are required to justify its inclusion into standard practice and provide evidence to support its efficacy.

Outcomes following renal transplantation in older people: a retrospective cohort study.

BACKGROUND: The mean age of renal transplant recipients is rising, with age no longer considered a contraindication. Outcomes in older patients have not, however, been fully defined. The aim of our study is to evaluate outcomes in older people following renal transplantation at a Scottish regional transplant unit. METHODS: All renal transplants from January 2001 to December 2010 were analysed (n = 762). Outcomes following renal transplantation in people over 65 years old were compared to those in younger patients. Outcome measures were: delayed graft function (DGF), primary non-function (PNF), biopsy proven acute rejection (BPAR), serum creatinine at 1 year and graft and recipient survival. Lengths of initial hospital stay and re-admission rates were also assessed. Student's T-Test was used to analyse continuous variables, Pearson's Chi-Squared test for categorical variables and the Kaplan-Meier estimator for survival analysis. RESULTS: Older recipients received proportionately more kidneys from older donors (27.1% vs. 6.3%; p < 0.001). Such kidneys were more likely to have DGF (40.7% vs. 16.9%; p < 0.001). Graft loss at 1 year was higher in kidneys from older donors (15.3% vs. 7.6%; p = 0.04). There was no significant difference in patient survival at 1 year based on the age of the donor kidney. Recipient age did not affect DGF (16.9% vs. 18.5%; p = 0.77) or graft loss at 1 year (11.9% vs. 7.8%; p = 0.28). Older recipients were, however, more likely to die in the first year post transplant (6.8% vs. 2.1%; p = 0.03). BPAR was less common in older patients (6.8% vs. 22%; p < 0.01). Older recipients were more likely to be readmitted to hospital (31.8% vs. 10.9%; p < 0.001). CONCLUSIONS: Older patients experience good outcomes following renal transplantation and donor or recipient age alone should not preclude this treatment. An awareness of this in clinicians managing older patients is important since the prevalence of End Stage Renal Disease is increasing in this age group.