Why is a liver with steatosis susceptible to cold ischemic injury?

Bortezomib enhances fatty liver preservation in Institut George Lopez-1 solution through adenosine monophosphate activated protein kinase and Akt/mTOR pathways

OBJECTIVES

The aim of this study is to investigate the protective mechanisms induced by bortezomib added to Institut George Lopez (IGL)-1 preservation solution to protect steatotic livers against cold ischaemia reperfusion injury and to examine whether these mechanisms occur through the activation of adenosine monophosphate activated protein kinase (AMPK), Akt/mTOR pathways.

METHODS

Steatotic livers from obese rats were preserved for 24 h (at 4 °C) in IGL-1 solution with or without bortezomib (100 nM) or pretreated with AMPK inhibitor adenine 9-α-D-arabinofuranoside and preserved in IGL-1 + bortezomib. Livers were then perfused for 2 h at 37 °C. Liver injury (alanine aminotransferase/aspartate aminotransferase) and function (bile production and vascular resistance) were measured. Also, Akt/mTOR, phosphorylated AMPK (pAMPK) and apoptosis were determined by Western blot analyses.

KEY FINDINGS

Bortezomib addition to IGL-1 solution significantly reduced steatotic liver injury, improved graft function and decreased liver apoptosis. These benefits were diminished by the pretreatment of obese rats with AMPK inhibitor Ara. Western blot analyses showed a significant increase in pAMPK after ischaemia and reperfusion. We also observed a significant phosphorylation of Akt in IGL-1 +bortezomib group that, in turn, induced the phosphorylation of mTOR and glycogen synthase kinase 3β.

CONCLUSIONS

Bortezomib, at low and non toxic concentration, is a promising additive to IGL-1 solution for steatotic liver preservation. Its protective effect is due to the activation of AMPK and Akt/mTOR pathways.

Decreased apoptosis in fatty livers submitted to subnormothermic machine-perfusion respect to cold storage

Machine perfusion at subnormothermic temperature (20°C), MP20, was developed by Vairetti et al. and showed to afford a better preservation of fatty livers respect to traditional cold storage (CS) in terms of enzyme release into the perfusate and bile, glycogen stores, energy charge and oxidative stress. Here we investigated whether it also caused decreased cell death by apoptosis. Fatty and lean Zucker rats were submitted to MP20 or CS for 6 h and reperfused normothermically for 2 h. Apoptotic cells were revealed by immunohistochemistry of activated caspase-3 and M30 (new epitope on CK18 degraded by caspase-3) and by the TUNEL assay. Portal pressure was also determined. A statistically significant reduction of hepatocyte apoptosis, but especially of sinusoidal cells was determined for fatty livers submitted to MP20 respect to CS. Portal pressure was significantly lower after MP20 respect to CS. The reduction of sinusoidal cell death by apoptosis without need for anti-apoptotic therapies appears particularly positive since apoptotic sinusoidal cells hinder microcirculation in the sinusoids and are thrombogenic. These results further confirm the potential of MP20 for preserving fatty livers that would be otherwise discarded as grafts, and thus for increasing the donor pool for liver transplantation.

Use of severely steatotic grafts in liver transplantation: a matched case-control study

BACKGROUND

Although there is a worldwide need to expand the pool of available liver grafts, cadaveric livers with severe steatosis (>60%) are discarded for orthotopic liver transplantation (OLT) by most centers.

METHODS

We analyzed patients receiving liver grafts with severe steatosis between January 2002 and September 2006. These patients were matched 1:2 with control patients without severe steatosis according to status the waiting list, recipient age, recipient body mass index (BMI), and model for end-stage liver disease (MELD) score. Primary end points were the incidence of primary graft nonfunction (PNF), and graft and patient survival. Secondary end points included primary graft dysfunction (PDF), the incidence of postoperative complications, and histologic assessment of steatosis in follow-up biopsies. We also conducted a survey on the use of grafts with severe steatosis among leading European liver transplant centers.

RESULTS

During the study period, 62 patients dropped out of the waiting list and 45 of them died due to progression of disease. Of 118 patients who received transplants 20 (17%) received a graft with severe steatosis during this period. The median degree of total liver steatosis was 90% (R = 65%-100%) for the steatotic group. The steatotic (n = 20) and matched control group (n = 40) were comparable in terms of recipient age, BMI, MELD score, and cold ischemia time. The steatotic group had a significantly higher rate of PDF and/or renal failure. Although the median intensive care unit (ICU) and hospital stay were not significantly different between both groups, the proportion of patients with long-term ICU (> or =21 days) and hospital (> or =40 days) stay was significantly higher for patients with a severely steatotic graft. Sixty-day mortality (5% vs. 5%) and 3-year patient survival rate (83% vs. 84%) were comparable between the control and severe steatosis group. Postoperative histologic assessment demonstrated that the median total amount of liver steatosis decreased significantly (median: 90% to 15%, P < 0.001). Our survey showed that all but one of the European centers currently reject liver grafts with severe steatosis for any recipient.

CONCLUSION

Due to the urgent need of liver grafts, severely steatotic grafts should be no longer discarded for OLT. Maximal effort must be spent when dealing with these high-risk organs but the use of severely steatotic grafts may save the lives of many patients who would die on the waiting list.

Safety limit of the extent of hepatectomy for rats with moderately fatty liver: experimental study concerning living liver donor safety

INTRODUCTION

The aim of the present study was to determine whether rats with moderately fatty liver could withstand a 90% hepatectomy, which rats with normal livers can survive.

MATERIAL AND METHODS

Nine-week-old male Wistar rats were used. Normal rat chow was fed to the normal liver group, and fat-enriched rat chow was fed to the fatty liver group for 4 weeks to induce a moderately fatty liver. The authors have previously reported that this fatty liver rat model can cause fatal liver dysfunction after reduced-size-liver transplantation. A 90% and 95% hepatectomy were performed using rats of both groups to evaluate posthepatectomized liver function.

RESULTS

All rats undergoing a 90% hepatectomy were still alive 30 days after the hepatectomy, but the rats that underwent a 95% hepatectomy were all dead within 4 days regardless of group. Increases in the liver remnant wet weight measured until 7 postoperative days after 90% hepatectomy were almost similar among the two groups. Alanin aminotransferase measured at 24, 48, 72, and 168 h after a 90% hepatectomy were significantly higher in the fatty liver group than in the normal liver group. Similarly, at up to 72 h postoperatively, the serum hyarulonic acids were significantly higher in the fatty liver group.

CONCLUSION

A moderately fatty liver did not cause mortality in 90% hepatectomized rats. However, it caused a higher degree of hepatic parenchymal as well as sinusoidal injury.

The effect of image colour distortion on evaluation of donor liver suitability for transplantation

Some medical applications rely on the use of colour in the diagnostic process, even when poor colour reproduction can affect diagnosis. In this paper, we investigate the effect colour distortion can have on assessment of livers for possible transplantation. We compare the diagnostic effects for the likely colour shifts when illuminant and camera remain uncalibrated or when a monitor is incorrectly calibrated. We describe methods that can result in accurate reproduction of image colour on visual displays and determine whether accurate colour reproduction is necessary for effective liver assessment.

L-carnitine ameliorates abnormal vulnerability of steatotic rat livers to cold ischemic preservation

BACKGROUND

Up to 30% of all livers retrieved for organ transplantation exhibit steatotic transformations. Chronic organ-donor shortage has led to the acceptance of these organs for transplantation, although a higher risk of graft nonfunction is associated with the preservation of steatotic livers.

METHODS

A dietary steatosis was induced in Wistar rats by fasting them for 2 days and feeding them with a fat-free diet. Fatty livers (n=14) were retrieved and flushed with 60 mL of histidine, tryptophane, alpha-ketoglutarate (HTK) solution. In half of the experiments, L-carnitine (5 mM) was added to the HTK. Functional integrity of the livers was evaluated by isolated reperfusion with KHB in a recirculating system at 37 degrees C for 45 minutes.

RESULTS

Addition of L-carnitine to the HTK promoted a significant reduction of the enzyme leakage from the livers upon reperfusion. Release of alanine-aminotransferase was reduced to one third (127+/-22 vs. 423+/-61 U/L), and the loss of glutamate dehydrogenase in the perfusate could be reduced significantly (42+/-7 vs. 542+/-134 U/L) when compared with livers stored without additional medication. Morphologic corroboration of these data was obtained by electron microscopy. Although normal appearance of liver mitochondria was preserved at the end of the cold ischemic storage, reperfusion of cold-stored fatty livers entailed massive alterations and frequent destruction of hepatic mitochondria. However, these morphologic impairments were remarkably mitigated in the carnitine-treated group.

CONCLUSIONS

L-carnitine represents a feasible metabolic adjunct for a safe and more successful preservation of ischemia-reperfusion-sensitive steatotic livers.

Prostaglandin E1 improved the function of transplanted fatty liver in a rat reduced-size-liver transplantation model under conditions of permissible cold preservation

The aim of this study was to determine whether the minimum necessary volume of a moderate fatty liver graft was similar to the normal liver volume and to elucidate means for improving the function of the transplanted fatty liver if it were inferior in volume to a normal liver under conditions of permissible cold preservation. Nine-week-old male Wistar rats were used. Normal rat chow was fed to the normal liver group, and fat-enriched rat chow was fed to the fatty liver group for 4 weeks to induce a moderately fatty liver. Liver transplantation with various volumes of reduced-size grafts, including whole liver graft (100%LT), 70% volume graft (70%LT), and 30% volume graft (30%LT), was performed with both groups of rats as donors. All procedures were performed under the conditions of 2-hour cold preservation. All rats with an implanted normal liver were surviving at 7 days after the operation regardless of the graft volume (100%LT, 5 of 5; 70%LT, 5 of 5; 30%LT, 5/5). In contrast, the survival rates decreased according to the graft volume in rats implanted with fatty livers (100%LT, 8 of 8; 70%LT, 5 of 8; 30%LT, 2/8). To improve the survival of 30%LT with fatty liver, we employed two potent inhibitors of ischemia-reperfusion injury: FK506 and prostaglandin E1. Though FK506 had no advantageous effect, prostaglandin E1 significantly improved the survival rate and diminished serum levels of alanine aminotransferase and hyaluronic acid. In conclusion, the volume of graft necessary for successful transplantation is larger in fatty livers than in normal livers in permissible cold preservation. Also, prostaglandin E1 protects grafts against ischemia-reperfusion injury and improves the functioning of a transplanted fatty liver.

N-acetilcisteína diminui a congestão hepática na lesão de isquemia e reperfusão: estudo experimental

OBJETIVOS: A isquemia tem sido utilizada na cirurgia hepática desde o início do século. Embora possibilite a diminuição da perda sangüínea durante as ressecções e a manutenção do órgão à espera de um transplante, a ausência de perfusão traz como conseqüência um dano ao órgão, que se amplifica por ocasião da sua reoxigenação. A N-Acetilcisteína é uma droga capaz de repor os estoques celulares de glutationa, um antioxidante fundamental no controle das lesões resultantes do restabelecimento da perfusão sangüínea, esperando-se dessa forma que diminua a lesão acima descrita. Com o propósito de avaliar a capacidade da N-Acetilcisteína reduzir o dano hepático, utilizou-se um modelo murino de isquemia e reperfusão normotérmica. MÉTODO: Foram utilizados vinte ratos Wistar fêmeas, divididos em dois grupos. No grupo tratado, 400mg/kg de N-Acetilcisteína foram administrados pela via intravenosa, 15 minutos antes do clampeamento do pedículo do lobo esquerdo por 90 minutos. No grupo controle foi administrado o volume equivalente de solução fisiológica. Foi estabelecido um período de quatro horas de reperfusão, após o qual os animais foram sacrificados para a realização de análise histopatológica do lobo esquerdo com coloração de Hematoxilina-Eosina. A lesão tecidual foi quantificada quanto à presença de congestão, esteatose e necrose. RESULTADOS: O estudo evidenciou a capacidade de a N-Acetilcisteína diminuir significativamente a congestão. Não houve diferenças quanto à presença de esteatose e necrose. CONCLUSÃO: Os resultados obtidos permitem-nos concluir que o uso prévio da N-Acetilcisteína nos processos de isquemia e reperfusão, em normotermia, é capaz de diminuir a congestão hepática. A N-Acetilcisteína não diminui a presença de esteatose e necrose.

A proposal for scoring marginal liver grafts

The aim of this study is to assess the effect of accumulation of marginal liver graft criteria on the immediate outcome of liver transplantation (LT). The last 325 consecutive LT performed in 293 patients were analyzed retrospectively with respect to donor acceptance criteria. A marginal liver score was elaborated on the basis of the following features: donor > 60 years, ICU stay > 4 days, cold ischemia times > 13 h, hypotensive episodes < 60 mmHg > 1 h, bilirubin > 2.0 mg/dl, ALT > 170 U/l, and AST > 140 U/l were scored with the value 1. The use of dopamine doses > 10 microg/kg per min and peak serum sodium > 155 mEq/l were labeled with value 2. The cut-off point at 6 months after LT revealed 42 deaths (14%), with 65 graft losses (20%) and 32 (9%) retransplants. Recipient survival was not affected by the combined effect of marginal criteria. However, recipients transplanted with marginal livers with score 3 or more showed a decrease in graft survival (log-rank 6.21; P = 0.045) and an increase in delayed non-function rate (10 out of 33 vs 4 out of 156; P = 0.03). The use of marginal liver donors with more than three risk factors must be carefully reviewed or refused because of the cumulative dysfunction of these grafts.