Xavier Stéphenne

Metformin activates AMP-activated protein kinase in primary human hepatocytes by decreasing cellular energy status.

Aim/hypothesisThe glucose-lowering drug metformin has been shown to activate hepatic AMP-activated protein kinase (AMPK), a master kinase regulating cellular energy homeostasis. However, the underlying mechanisms remain controversial and have never been investigated in primary human hepatocytes.MethodsHepatocytes isolated from rat, mouse and human livers were treated with various concentrations of metformin. Isoform-specific AMPKα abundance and activity, as well as intracellular adenine nucleotide levels and mitochondrial oxygen consumption rates were determined at different time points.ResultsMetformin dose- and time-dependently increased AMPK activity in rat and human hepatocytes, an effect associated with a significant rise in cellular AMP:ATP ratio. Surprisingly, we found that AMPKα2 activity was undetectable in human compared with rat hepatocytes, while AMPKα1 activities were comparable. Accordingly, metformin only increased AMPKα1 activity in human hepatocytes, although both AMPKα isoforms were activated in rat hepatocytes. Analysis of mRNA expression and protein levels confirmed that only AMPKα1 is present in human hepatocytes; it also showed that the distribution of β and γ regulatory subunits differed between species. Finally, we demonstrated that the increase in AMP:ATP ratio in hepatocytes from liver-specific Ampkα1/2 (also known as Prkaa1/2) knockout mice and humans is due to a similar and specific inhibition of the mitochondrial respiratory-chain complex 1 by metformin.Conclusions/interpretationActivation of hepatic AMPK by metformin results from a decrease in cellular energy status owing to metformin’s AMPK-independent inhibition of the mitochondrial respiratory-chain complex 1. The unique profile of AMPK subunits found in human hepatocytes should be considered when developing new pharmacological agents to target the kinase.

Cryopreserved liver cell transplantation controls ornithine transcarbamylase deficient patient while awaiting liver transplantation.

Liver cell transplantation was performed in a child with urea cycle disorder poorly equilibrated by conventional therapy as a bridge to transplantation. A 14‐month‐old boy with ornithine transcarbamylase (OTC) deficiency received 0.24 billion viable cryopreserved cells/kg over 16 weeks. Tacrolimus and steroids were given as immunosuppressive treatment while the patient was kept on the pre‐cell transplant therapy. Mean blood ammonia level decreased significantly following the seven first infusions, while urea levels started to increase from undetectable values. After those seven infusions, an ammonium peak up to 263 μg/dL, clinically well tolerated, was observed. Interestingly, blood urea levels increased continuously to reach 25 mg/dL, after the last three infusions. Eventually, he benefited from elective orthotopic liver transplantation (OLT) and the post‐surgical course was uneventful. We conclude that use of cryopreserved cells allowed short‐ to medium‐term metabolic control and urea synthesis in this male OTC‐deficient patient while waiting for OLT.

Management of familial hypercholesterolemia in children and young adults: Consensus paper developed by a panel of lipidologists, cardiologists, paediatricians, nutritionists, gastroenterologists, general practitioners and a patient organization

UNLABELLED Since heterozygous familial hypercholesterolemia (HeFH) is a disease that exposes the individual from birth onwards to severe hypercholesterolemia with the development of early cardiovascular disease, a clear consensus on the management of this disease in young patients is necessary. In Belgium, a panel of paediatricians, specialists in (adult) lipid management, general practitioners and representatives of the FH patient organization agreed on the following common recommendations. 1. Screening for HeFH should be performed only in children older than 2 years when HeFH has been identified or is suspected (based on a genetic test or clinical criteria) in one parent.2. The diagnostic procedure includes, as a first step, the establishment of a clear diagnosis of HeFH in one of the parents. If this precondition is satisfied, a low-density-lipoprotein cholesterol (LDL-C) levelabove 3.5 mmol/L (135 mg/dL) in the suspected child is predictive for differentiating affected from non-affected children. 3. A low saturated fat and low cholesterol diet should be started after 2 years, under the supervision of a dietician or nutritionist.4. The pharmacological treatment, using statins as first line drugs, should usually be started after 10 years if LDL-C levels remain above 5 mmol/L (190 mg/dL), or above 4 mmol/L (160 mg/dL) in the presence of a causative mutation, a family history of early cardiovascular disease or severe risk factors. The objective is to reduce LDL-C by at least 30% between 10 and 14 years and, thereafter, to reach LDL-C levels of less than 3.4 mmol/L (130 mg/dL). CONCLUSION The aim of this consensus statement is to achieve more consistent management in the identification and treatment of children with HeFH in Belgium.

Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection in children and adolescents.

BACKGROUND & AIMS This multi-center study aimed to prospectively evaluate the safety and efficacy of a genotype-based Pegylated Interferon alfa-2a/Ribavirin therapy in treatment-naïve hepatitis C virus (HCV), positive HCV serology, and quantifiable HCV RNA, infected children. METHODS Eighteen children with genotypes 2 and 3 patients (group A) were assigned to medication for 24weeks, and 47 children with genotypes 1, 4, 5 and 6 patients (group B) for 48weeks. RESULTS Early response at week 12 was observed in 83% of group A patients and in 57% of group B patients (p<0.05). End of treatment response was achieved in 94% of patients in group A and in 57% in group B (p<0.001). Sustained virologic response was maintained in 89% of patients in group A and in 57% of patients in group B (p<0.01). Ten patients stopped prematurely the treatment, 2 for serious adverse event (acute hepatitis and thyrotoxicosis), and 8 because of no virologic response at week 24. Peginterferon alfa-2a and Ribavirin dose was adjusted in 15 patients (23%), 11 for neutropenia (17%), and 3 patients (5%), for anemia, respectively. Treatment-related adverse events included fever and flu-like symptoms (54%), irritability-depression-change of mood (34%), vomiting (23%), abdominal pain (38%), loss of appetite (21.5%) and dermatitis (29%). No influence on height growth was observed. CONCLUSIONS Pegylated inteferon alfa-2a and Ribavirin treatment allowed to achieve SVR in 57% of pediatric patients with genotypes 1, 4, 5 and 6, and in 94% of genotypes 2 and 3. These results show an improved SVR as compared to reference series in adults with similar regimen.

Cryopreservation of human hepatocytes alters the mitochondrial respiratory chain complex 1.

Transplantation of human hepatocytes has recently been demonstrated as a safe alternative to partially correct liver inborn errors of metabolism. Cryopreservation remains the most appropriate way of cell banking. However, mitochondrial-mediated apoptosis has been reported after cryopreservation and little is known on the involved molecular mechanisms. The aim of this study was to investigate mitochondrial functions of freshly isolated and cryopreserved/thawed hepatocytes from mice and humans. We report here that cryopreservation induced a dramatic drop of ATP levels in hepatocytes. The oxygen consumption rate of cryopreserved/thawed hepatocytes was significantly lower compared to fresh cells. In addition, the uncoupling effect of 2,4-dinitrophenol was lost, in parallel with a reduction of mitochondrial membrane potential. Furthermore, a decrease in mitochondrial respiratory rate was evidenced on permeabilized hepatocytes in the presence of substrate for the respiratory chain complex 1. Interestingly, this effect was less marked with a substrate for complex 2. Electron microscopy examination indicated that mitochondria were swollen and devoid of cristae after cryopreservation. These changes could explain the cytosolic release of the proapoptotic protein cytochrome c in cryopreserved cells. Nevertheless, no caspase 9-3 activation and only few apoptotic and necrotic cells were found, indicating that the subsequent cell death program was not yet evidenced. Our results demonstrate that cryopreservation of hepatocytes induced alteration of the mitochondrial machinery. They also suggest that, in addition to technical progress in the cryopreservation procedure, protection of the respiratory chain complex 1 should be considered to improve the quality of cryopreserved hepatocytes.

Tissue factor‐dependent procoagulant activity of isolated human hepatocytes: Relevance to liver cell transplantation

Liver cell transplantation (LCT) aims to correct inborn liver function defects by infusing metabolically active cells into the diseased liver. Further improvement in LCT might depend on the prevention of early loss of transplanted cells. As tissue factor (TF)‐dependent activation of coagulation was found to contribute to a low rate of beta cell engraftment in islet transplantation, we investigated the potential procoagulant activity (PCA) of hepatocyte preparations. TF expression on hepatocyte preparations was assessed by flow cytometry, reverse‐transcription polymerase chain reaction and immunofluorescence. PCA depending on TF was evaluated in human plasma and in whole blood systems. Coagulation parameters were followed by routine techniques in a LCT recipient Crigler‐Najjar patient. We determined that hepatocytes express soluble and membrane‐bound forms of TF. We showed that hepatocytes exert a TF‐dependent PCA. In parallel, delayed increase in D‐dimer levels was observed following the hepatocyte infusions in the Crigler‐Najjar patient. Furthermore, in vitro experiments demonstrated that TF‐dependent PCA of hepatocytes is inhibited by N‐acetyl‐L‐cysteine. In conclusion, hepatocytes exert TF‐dependent PCA, which may contribute to early loss of infused cells. Addition of N‐acetyl‐L‐cysteine to the suspensions of hepatocytes might be beneficial in LCT by inhibiting activation of coagulation. Liver Transpl 13:599–606, 2007.

Permanent access to the portal system for cellular transplantation using an implantable port device.

A novel application of the implantable Port‐a‐Cath (PAC) system is described in the context of cellular transplantation. A silicone catheter was inserted in a collateral branch of the portal vein and connected to a port device positioned subcutaneously on the left thoracic cage. This permanent vascular access allowed iterative intraportal infusions of allogenic hepatocytes without the need of repeated transhepatic catheterization of the portal vein. Using this technique, repeated infusions of cryopreserved and / or fresh hepatocytes were successfully carried out in 3 children with inborn errors of liver metabolism, with the aim of progressively providing a sufficient mass of transplanted liver cells to stabilize the metabolic condition of the patients. We suggest that this technique might also be valuable in pancreatic islet cell transplantation. (Liver Transpl 2004;10:1213–1215.)

Chronic hepatitis B in children and adolescents

Hepatitis B virus (HBV) infection is still one of the most important causes of liver disease, with 2 billion people infected worldwide and more than 600,000 deaths each year, caused in 94% of cases by chronic infection-related cirrhosis and hepatocellular carcinoma (HCC) [1–3]. The World Health Organization (WHO) estimates more than 360 million persons being chronic carriers worldwide (6% of the world population). The incidence of HBV infection has been declining over the last two decades thanks to the introduction of universal immunization programs and the implementation of blood-donor screening. Nevertheless, a significant number of adults and children are still infected each year, the latter often developing chronic infection and requiring an appropriate follow-up. In spite of a rather benign course of chronic disease during childhood and adolescence, HBV chronic carriers have a lifetime risk of developing HCC up to 25%, and an incidence of cirrhosis of 2–3% per year [4]. Safe and partially effective antiviral therapies are available, but few are licensed for use in children, and an accurate selection of subjects to treat and of the right timing for treatment is needed to optimize efficacy and reduce viral resistance. 2012 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Bivalirudin in Combination with Heparin to Control Mesenchymal Cell Procoagulant Activity

Islet and hepatocyte transplantation are associated with tissue factor-dependent activation of coagulation which elicits instant blood mediated inflammatory reaction, thereby contributing to a low rate of engraftment. The aim of this study was i) to evaluate the procoagulant activity of human adult liver-derived mesenchymal progenitor cells (hALPCs), ii) to compare it to other mesenchymal cells of extra-hepatic (bone marrow mesenchymal stem cells and skin fibroblasts) or liver origin (liver myofibroblasts), and iii) to determine the ways this activity could be modulated. Using a whole blood coagulation test (thromboelastometry), we demonstrated that all analyzed cell types exhibit procoagulant activity. The hALPCs pronounced procoagulant activity was associated with an increased tissue factor and a decreased tissue factor pathway inhibitor expression as compared with hepatocytes. At therapeutic doses, the procoagulant effect of hALPCs was inhibited by neither antithrombin activators nor direct factor Xa inhibitor or direct thrombin inhibitors individually. However, concomitant administration of an antithrombin activator or direct factor Xa inhibitor and direct thrombin inhibitor proved to be a particularly effective combination for controlling the procoagulant effects of hALPCs both in vitro and in vivo. The results suggest that this dual antithrombotic therapy should also improve the efficacy of cell transplantation in humans.

Hepatocyte transplantation using the domino concept in a child with Tetrabiopterin non-responsive phenylketonuria.

Phenylketonuria is a metabolic disease caused by phenylalanine hydroxylase deficiency. Treatment is based on a strict natural protein-restricted diet that is associated with the risk of malnutrition and severe psychosocial burden. Oral administration of tetrahydrobiopterin can increase residual enzyme activity, but most patients with severe clinical phenotypes are nonresponders. We performed liver cell transplantation in a 6-year-old boy with severe tetrahydrobiopterin nonresponsive phenylketonuria who failed to comply with diet prescriptions. The transplanted hepatocytes were obtained in part from an explanted glycogen storage type 1b liver. Following two infusions, blood phenylalanine levels returned within the therapeutic target while the phenylalanine half-life assessed by loading tests decreased from 43 to 19 h. However, 3 months later, blood phenylalanine concentrations increased and the phenylalanine intake had to be reduced. Cell-based therapy is a promising therapeutic option in phenylketonuria, and the domino concept may solve the issue of cell sources for hepatocyte transplantation.