Jef Verbeek

Pharmacological Inhibition of Poly(ADP-Ribose) Polymerases Improves Fitness and Mitochondrial Function in Skeletal Muscle

We previously demonstrated that the deletion of the poly(ADP-ribose)polymerase (Parp)-1 gene in mice enhances oxidative metabolism, thereby protecting against diet-induced obesity. However, the therapeutic use of PARP inhibitors to enhance mitochondrial function remains to be explored. Here, we show tight negative correlation between Parp-1 expression and energy expenditure in heterogeneous mouse populations, indicating that variations in PARP-1 activity have an impact on metabolic homeostasis. Notably, these genetic correlations can be translated into pharmacological applications. Long-term treatment with PARP inhibitors enhances fitness in mice by increasing the abundance of mitochondrial respiratory complexes and boosting mitochondrial respiratory capacity. Furthermore, PARP inhibitors reverse mitochondrial defects in primary myotubes of obese humans and attenuate genetic defects of mitochondrial metabolism in human fibroblasts and C. elegans. Overall, our work validates in worm, mouse, and human models that PARP inhibition may be used to treat both genetic and acquired muscle dysfunction linked to defective mitochondrial function.

Roux-en-y gastric bypass attenuates hepatic mitochondrial dysfunction in mice with non-alcoholic steatohepatitis

Objective No therapy for non-alcoholic steatohepatitis (NASH) has been approved so far. Roux-en-y gastric bypass (RYGB) is emerging as a therapeutic option, although its effect on NASH and related hepatic molecular pathways is unclear from human studies. We studied the effect of RYGB on pre-existent NASH and hepatic mitochondrial dysfunction—a key player in NASH pathogenesis—in a novel diet-induced mouse model nicely mimicking human disease. Design C57BL/6J mice were fed a high-fat high-sucrose diet (HF-HSD). Results HF-HSD led to early obesity, insulin resistance and hypercholesterolaemia. HF-HSD consistently induced NASH (steatosis, hepatocyte ballooning and inflammation) with fibrosis already after 12-week feeding. NASH was accompanied by hepatic mitochondrial dysfunction, characterised by decreased mitochondrial respiratory chain (MRC) complex I and IV activity, ATP depletion, ultrastructural abnormalities, together with higher 4-hydroxynonenal (HNE) levels, increased uncoupling protein 2 (UCP2) and tumour necrosis factor-α (TNF-α) mRNA and free cholesterol accumulation. In our model of NASH and acquired mitochondrial dysfunction, RYGB induced sustained weight loss, improved insulin resistance and inhibited progression of NASH, with a marked reversal of fibrosis. In parallel, RYGB preserved hepatic MRC complex I activity, restored ATP levels, limited HNE production and decreased TNF-α mRNA. Conclusions Progression of NASH and NASH-related hepatic mitochondrial dysfunction can be prevented by RYGB. RYGB preserves respiratory chain complex activity, thereby restoring energy output, probably by limiting the amount of oxidative stress and TNF-α. These data suggest that modulation of hepatic mitochondrial function contributes to the favourable effect of RYBG on established NASH.

Clinical differences between early-onset HELLP syndrome and early-onset preeclampsia during pregnancy and at least 6 months postpartum

OBJECTIVE We sought to evaluate whether clinical and laboratory variables differ between former patients who had HELLP syndrome and former patients who had preeclampsia (PE) without HELLP. STUDY DESIGN We compared early-onset HELLP (n = 75) with early-onset PE (n = 40) with respect to clinical features during the hypertensive complication and to metabolic, hemodynamic, and hemostatic variables determined at least 6 months postpartum. RESULTS HELLP differed from PE by a borderline higher frequency of eclampsia (13% vs 3%) during the complication, and by a lower prevalence of hypertension (19% vs 33%), proteinuria (2% vs 23%), thrombophilia (6% vs 27%), obesity (9% vs 33%), hypertriglyceridemia (1% vs 15%), hyperglycemia (0% vs 11%), and elevated levels of fasting homocysteine (6% vs 21%) at least 6 months postpartum. CONCLUSION Women with HELLP had fewer signs of abnormalities consistent with the metabolic syndrome and a 4-fold lower prevalence of thrombophilia as compared with PE women without HELLP.

The plant decapeptide OSIP108 prevents copper-induced apoptosis in yeast and human cells

We previously identified the Arabidopsis thaliana-derived decapeptide OSIP108, which increases tolerance of plants and yeast cells to oxidative stress. As excess copper (Cu) is known to induce oxidative stress and apoptosis, and is characteristic for the human pathology Wilson disease, we investigated the effect of OSIP108 on Cu-induced toxicity in yeast. We found that OSIP108 increased yeast viability in the presence of toxic Cu concentrations, and decreased the prevalence of Cu-induced apoptotic markers. Next, we translated these results to the human hepatoma HepG2 cell line, demonstrating anti-apoptotic activity of OSIP108 in this cell line. In addition, we found that OSIP108 did not affect intracellular Cu levels in HepG2 cells, but preserved HepG2 mitochondrial ultrastructure. As Cu is known to induce acid sphingomyelinase activity of HepG2 cells, we performed a sphingolipidomic analysis of OSIP108-treated HepG2 cells. We demonstrated that OSIP108 decreased the levels of several sphingoid bases and ceramide species. Moreover, exogenous addition of the sphingoid base dihydrosphingosine abolished the protective effect of OSIP108 against Cu-induced cell death in yeast. These findings indicate the potential of OSIP108 to prevent Cu-induced apoptosis, possibly via its effects on sphingolipid homeostasis.

The plant decapeptide OSIP108 prevents copper-induced toxicity in various models for Wilson disease.

BACKGROUND Wilson disease (WD) is caused by accumulation of excess copper (Cu) due to a mutation in the gene encoding the liver Cu transporter ATP7B, and is characterized by acute liver failure or cirrhosis and neuronal cell death. We investigated the effect of OSIP108, a plant derived decapeptide that prevents Cu-induced apoptosis in yeast and human cells, on Cu-induced toxicity in various mammalian in vitro models relevant for WD and in a Cu-toxicity zebrafish larvae model applicable to WD. METHODS The effect of OSIP108 was evaluated on viability of various cell lines in the presence of excess Cu, on liver morphology of a Cu-treated zebrafish larvae strain that expresses a fluorescent reporter in hepatocytes, and on oxidative stress levels in wild type AB zebrafish larvae. RESULTS OSIP108 increased not only viability of Cu-treated CHO cells transgenically expressing ATP7B and the common WD-causing mutant ATP7B(H1069Q), but also viability of Cu-treated human glioblastoma U87 cells. Aberrancies in liver morphology of Cu-treated zebrafish larvae were observed, which were further confirmed as Cu-induced hepatotoxicity by liver histology. Injections of OSIP108 into Cu-treated zebrafish larvae significantly increased the amount of larvae with normal liver morphology and decreased Cu-induced production of reactive oxygen species. CONCLUSIONS OSIP108 prevents Cu-induced toxicity in in vitro models and in a Cu-toxicity zebrafish larvae model applicable to WD. GENERAL SIGNIFICANCE All the above data indicate the potential of OSIP108 as a drug lead for further development as a novel WD treatment.

An Overview of Mouse Models of Nonalcoholic Steatohepatitis: From Past to Present

Non‐alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the Western world. It is associated with obesity and type 2 diabetes and represents a spectrum of histological abnormalities ranging from simple steatosis to non‐alcoholic steatohepatitis (NASH), which can further progress to fibrosis, cirrhosis, hepatocellular carcinoma (HCC), and liver failure. To gain insight into the pathogenesis and evaluate treatment options, mouse models of NAFLD/NASH are of utmost importance. There is a high phenotypical variety in the available mouse models, however, models that truly display the full spectrum of histopathological and metabolic features associated with human NASH are rare. In this review, we summarize the most important NAFLD/NASH mouse models that have been developed over the years and briefly highlight the pros and cons. Also, we illustrate the preclinical research in which these models have been used.

Hair ethyl glucuronide and serum carbohydrate deficient transferrin for the assessment of relapse in alcohol-dependent patients

OBJECTIVES Ethyl glucuronide in hair (hEtG) and serum carbohydrate deficient transferrin (%CDT) are valuable markers for alcohol abuse, but their diagnostic accuracy to monitor abstinence and relapse is unclear. Here, we investigate to what extent repeated measurements of hEtG and %CDT can be used to monitor relapse in alcohol-dependent patients during abstinence treatment. DESIGN AND METHODS HEtG and %CDT were measured in individuals starting treatment for alcohol dependence both at treatment entry and 3months later. Alcohol consumption and relapse episodes were recorded using the Time Line Follow Back and by alcohol breath and urine tests, and correlated with hEtG and %CDT measurements. RESULTS Fifteen patients completed the study, of which nine had one or more relapses. Hair EtG and serum %CDT identified whether a relapse occurred in 78% and 57% of cases, respectively. Only hEtG correlated with the amount of alcohol consumed before treatment entry (Pearson r=0.92; p<0.001). The specificity of %CDT to assess abstinence during treatment was 100%. HEtG had a specificity of only 17%; however, in all patients who remained abstinent, hEtG decreased with >85% from initial values. Mean hEtG, but not %CDT, differed significantly between patients who relapsed and patients who remained abstinent (p=0.034). CONCLUSIONS HEtG was more sensitive than serum %CDT to assess relapse in alcohol-dependent patients and was positively correlated with the amounts of alcohol consumed. In contrast, serum %CDT was more specific for assessing abstinence. We highlight the benefit of repeated measurements of hEtG and serum %CDT for monitoring abstinence during treatment.

Development of a Representative Mouse Model with Nonalcoholic Steatohepatitis.

Non‐alcoholic fatty liver disease (NAFLD) is the most prevalent liver disease in the Western world. It represents a disease spectrum ranging from isolated steatosis to non‐alcoholic steatohepatitis (NASH). In particular, NASH can evolve to fibrosis, cirrhosis, hepatocellular carcinoma, and liver failure. The development of novel treatment strategies is hampered by the lack of representative NASH mouse models. Here, we describe a NASH mouse model, which is based on feeding non–genetically manipulated C57BL6/J mice a ‘Western style’ high‐fat/high‐sucrose diet (HF‐HSD). HF‐HSD leads to early obesity, insulin resistance, and hypercholesterolemia. After 12 weeks of HF‐HSD, all mice exhibit the complete spectrum of features of NASH, including steatosis, hepatocyte ballooning, and lobular inflammation, together with fibrosis in the majority of mice. Hence, this model closely mimics the human disease. Implementation of this mouse model will lead to a standardized setup for the evaluation of (i) underlying mechanisms that contribute to the progression of NAFLD to NASH, and (ii) therapeutic interventions for NASH.

Ethyl Glucuronide in Hair Is an Accurate Biomarker of Chronic Excessive Alcohol Use in Patients With Alcoholic Cirrhosis

*Department of Gastroenterology & Hepatology, University Hospitals KU Leuven, Leuven, Belgium; Division of Gastroenterology & Hepatology, Department of Internal Medicine, Maastricht University Medical Center, Maastricht, the Netherlands; Toxicological Center, University of Antwerp, Antwerp, Belgium; kDepartment of Psychiatry, University Hospital Brussels, Brussels, Belgium; Department of Nuclear Medicine and Molecular Imaging, University Hospitals KU Leuven, Leuven, Belgium; Department of Gastroenterology & Hepatology, University Hospital of Antwerp, Antwerp, Belgium; **TDM and Toxicology Laboratory, ZNA Stuivenberg, Antwerp, Belgium; Department of Abdominal Transplantation Surgery, University Hospitals KU Leuven, Leuven, Belgium; Department of Pathology, University Hospitals KU Leuven, Leuven, Belgium

Lower Limbic Metabotropic Glutamate Receptor 5 Availability in Alcohol Dependence

Animal studies suggest an important role for the metabotropic glutamate receptor subtype 5 (mGlu5) in the pathophysiology of alcohol dependence, but direct human evidence is lacking. The goal of this study was to investigate cerebral mGlu5 availability in alcohol-dependent subjects versus controls using 18F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (18F-FPEB) PET. Methods: Dynamic 90-min 18F-FPEB scans combined with arterial blood sampling were acquired for 16 recently abstinent alcohol-dependent subjects and 32 age-matched controls. Regional mGlu5 availability was quantified by the 18F-FPEB total distribution volume using both a voxel-by-voxel and a volume-of-interest analysis with partial-volume effect correction. Alcohol consumption within the last 3 mo was assessed by questionnaires and by hair ethyl glucuronide analysis. Craving was assessed using the Desire for Alcohol Questionnaire. Results: mGlu5 availability was lower in mainly limbic regions of alcohol-dependent subjects than in controls (P < 0.05, familywise error–corrected), ranging from 14% in the posterior cingulate cortex to 36% in the caudate nucleus. Lower mGlu5 availability was associated with higher hair ethyl glucuronide levels for most regions and was related to a lower level of craving specifically in the middle frontal gyrus, cingulate cortex, and inferolateral temporal lobe. Conclusion: These findings provide human in vivo evidence that limbic mGlu5 has a role in the pathophysiology of alcohol dependence, possibly involved in a compensatory mechanism helping to reduce craving during abstinence.