Isabelle A Leclercq

Catholic University of Louvain, Walloon Region, Belgium

Are you Isabelle A Leclercq?

Claim your profile

Publications (109)572.79 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Non-alcoholic fatty liver (steatosis) and steatohepatitis (NASH) are hepatic complications of metabolic syndrome. Endoplasmic reticulum (ER) stress is proposed as a crucial disease mechanism in obese and insulin resistant animals (such as ob/ob mice) with simple steatosis but its role in NASH remains controversial. We therefore evaluated the role of ER stress as a disease mechanism in foz/foz mice, which develop both the metabolic and the histological features that mimic human NASH. We explored ER stress markers in the liver of foz/foz mice in response to high-fat diet (HFD) after several time points. We then evaluated the effect of treatment with ER stress inducer tunicamycin, or conversely with ER protectant tauro-ursodeoxycholic acid (TUDCA) on the metabolic and hepatic features. Foz/foz mice are obese, glucose intolerant and develop NASH characterized by steatosis, inflammation, ballooned hepatocytes and apoptosis from 6 weeks of HFD feeding. This was not associated with activation of the upstream unfolded protein response (phospho-eIF2α, IRE1α activity, spliced Xbp1). Activation of JNK and up-regulation of Atf4 and Chop transcripts were however compatible with a "pathologic" response to ER stress. We tested it by intervention experiments. Induction of chronic ER stress failed to worsen obesity, glucose intolerance and NASH pathology in HFD-fed foz/foz mice. In addition, ER protectant TUDCA, although reducing steatosis, failed to improve glucose intolerance, hepatic inflammation and apoptosis in HFD-fed foz/foz mice. These results show that signals driving hepatic inflammation, apoptosis and insulin resistance are independent of ER stress in obese, diabetic mice with steatohepatitis.
    Clinical Science 04/2014; · 4.86 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Liver-specific overexpression of the insulin-like growth factor 2 (IGF2) mRNA binding protein p62/IGF2BP2-2 induces a fatty liver, which highly expresses IGF2. Since IGF2 expression is elevated in patients with steatohepatitis, the aim of our study was to elucidate the role and interconnection of p62 and IGF2 in lipid metabolism. Expression of p62 and IGF2 highly correlated in human liver disease. p62 induced an elevated ratio of C18:C16 and increased ELOVL fatty acid elongase 6 (ELOVL6) protein, the enzyme catalyzing the elongation of C16 to C18 fatty acids and promoting nonalcoholic steatohepatitis in mice and humans. p62 overexpression induced the activation of the ELOVL6 transcriptional activator SREBF1. Recombinant IGF2 induced the nuclear translocation of sterol regulatory element binding transcription factor 1 (SREBF1) and a neutralizing IGF2 antibody reduced ELOVL6 and mature SREBF1 protein levels. Concordantly, p62 and IGF2 correlated with ELOVL6 in human livers. Decreased palmitoyl-CoA levels as found in p62 tg livers can explain the lipogenic action of ELOVL6. Accordingly, p62 represents an inducer of hepatic C18 fatty acid production via a SREBF1-dependent induction of ELOVL6. These findings underline the detrimental role of p62 in liver disease.
    The Journal of Lipid Research 04/2014; · 4.39 Impact Factor
  • N Lanthier, I A Leclercq
    Hepatology 01/2014; · 12.00 Impact Factor
  • Nicolas Lanthier, Isabelle Leclercq
    [Show abstract] [Hide abstract]
    ABSTRACT: In the context of obesity, white adipocyte hypertrophy and adipose tissue macrophage infiltration result in the production of pro-inflammatory adipocytokines inducing insulin resistance locally but also in distant organs and contributing to low grade inflammatory status associated with the metabolic syndrome. Visceral adipose tissue is believed to play a prominent role. Brown and beige adipose tissues are capable of energy dissipation, but also of cytokine production and their role in dysmetabolic syndrome is emerging. This review focuses on metabolic and inflammatory changes in these adipose depots and contribution to metabolic syndrome. Also we will review surgical and pharmacological procedures to target adiposity as therapeutic interventions to treat obesity-associated disorders.
    Best Practice & Research Clinical Gastroenterology. 01/2014;
  • Journal of Hepatology 07/2013; · 9.86 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Alcohol consumption is a major cause of liver disease. It also associates with increased cardiovascular risk and type 2 diabetes. Alcoholic liver diseases (ALD) and non-alcoholic fatty liver diseases (NAFLD) share pathologic features, pathogenic mechanisms and pattern of disease progression. In NAFLD, steatosis, lipotoxicity and liver inflammation participate to hepatic insulin resistance. Our aim here is to verify the effect of alcohol on hepatic insulin sensitivity and to evaluate the role of alcohol-induced steatosis and inflammation on glucose homeostasis. Results : C57BL/6J mice were fed for 20 days a modified Lieber-DeCarli diet in which alcohol concentration was gradually increased up to 35% of daily caloric intake. Alcohol-fed mice show liver steatosis and inflammatory infiltration. OH-fed mice developed insulin resistance in the liver but not in muscles, as demonstrated by euglycemic-hyperinsulinemic clamp and analysis of the insulin signaling cascade. Treatment with the PPAR-α agonist Wy14,643 protected against OH-induced steatosis and Kupffer cell (KC) activation and almost abolished OH-induced insulin resistance. As KC activation may modulate insulin sensitivity, we repeated the clamp studies in mice depleted in KC to decipher the role of macrophages. Depletion of KC using liposomes-encapsuled clodronate in OH-fed mice failed both to improve hepatic steatosis and to restore insulin sensitivity as assessed by clamp. Conclusions : Our study shows that chronic alcohol consumption induces steatosis, Kuffer cell activation and hepatic insulin resistance in mice. PPAR-α agonist treatment that prevents steatosis and dampens hepatic inflammation also prevents alcohol-induced hepatic insulin resistance. However, Kupffer cell depletion little impacts on OH-induced metabolic disturbances.
    Clinical Science 06/2013; · 4.86 Impact Factor
  • Article: Reply.
    Gastroenterology 05/2013; · 12.82 Impact Factor
  • Gut 03/2013; · 10.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ras activation is a frequent event in human hepatocarcinoma that may contribute to resistance towards apoptosis. Salirasib is a ras and mTOR inhibitor that induces a pro-apoptotic phenotype in human hepatocarcinoma cell lines. In this work, we evaluate whether salirasib sensitizes those cells to TRAIL-induced apoptosis. Cell viability, cell death and apoptosis were evaluated in vitro in HepG2, Hep3B and Huh7 cells treated with DMSO, salirasib and YM155 (a survivin inhibitor), alone or in combination with recombinant TRAIL. Our results show that pretreatment with salirasib sensitized human hepatocarcinoma cell lines, but not normal human hepatocytes, to TRAIL-induced apoptosis. Indeed, FACS analysis showed that 25 (Huh7) to 50 (HepG2 and Hep3B) percent of the cells treated with both drugs were apoptotic. This occurred through activation of the extrinsic and the intrinsic pathways, as evidenced by a marked increase in caspase 3/7 (five to ninefold), caspase 8 (four to sevenfold) and caspase 9 (eight to 12-fold) activities in cells treated with salirasib and TRAIL compared with control. Survivin inhibition had an important role in this process and was sufficient to sensitize hepatocarcinoma cells to apoptosis. Furthermore, TRAIL-induced apoptosis in HCC cells pretreated with salirasib was dependent on activation of death receptor (DR) 5. In conclusion, salirasib sensitizes hepatocarcinoma cells to TRAIL-induced apoptosis by a mechanism involving the DR5 receptor and survivin inhibition. These results in human hepatocarcinoma cell lines and primary hepatocytes provide a rationale for testing the combination of salirasib and TRAIL agonists in human hepatocarcinoma.
    Cell Death & Disease 01/2013; 4:e471. · 6.04 Impact Factor
  • Isabelle A Leclercq
    Journal of Gastroenterology and Hepatology 11/2012; 27(11):1651-3. · 3.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND & AIMS: Self-renewal of mature hepatocytes promotes homeostasis and regeneration of adult liver. However, recent studies have indicated that liver progenitor cells (LPC) could give rise to hepatic epithelial cells during normal turnover of the liver and after acute injury. We investigated the capacity of LPC to differentiate into hepatocytes in vivo and contribute to liver regeneration. METHODS: We performed lineage tracing experiments, using mice that express tamoxifen-inducible Cre recombinase under control of osteopontin regulatory region crossed with yelow fluorescent protein reporter mice, to follow the fate of LPC and biliary cells. Adult mice received partial (two-thirds) hepatectomy, acute or chronic administration of carbon tetrachloride (CCl(4)), choline-deficient diet supplemented with ethionine, or 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet. RESULTS: LPC and/or biliary cells generated 0.78% and 2.45% of hepatocytes during and upon recovery of mice from liver injury, respectively. Repopulation efficiency by LPC and/or biliary cells increased when extracellular matrix and laminin deposition were reduced. The newly formed hepatocytes integrated into hepatic cords, formed biliary canaliculi, expressed hepato-specific enzymes, accumulated glycogen, and proliferated in response to partial hepatectomy, as neighboring native hepatocytes. By contrast, LPC did not contribute to hepatocyte regeneration during normal liver homeostasis, in response to surgical or toxic loss of liver mass, during chronic liver injury (CCl(4)-induced), or during ductular reactions. CONCLUSIONS: LPC or biliary cells terminally differentiate into functional hepatocytes in mice with liver injury.
    Gastroenterology 08/2012; · 12.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To investigate which transmembrane choline transporters and intracellular choline kinases play a prominent role at gene expression level in the rise of the total choline (tCho) peak at proton MR spectra in a rodent rhabdomyosarcoma model. Twenty-two rats bearing grafted bilateral syngenic rhabdomyosarcoma were examined on a clinical 3 T MR system. Total choline concentration was measured from proton MR spectra using cubic centimeter volumes of interest (VOIs) located contiguously along the greater axis of the tumour. After euthanasia, cubic centimetre tissue specimens corresponding to Proton magnetic resonance spectroscopy (H-MRS) VOIs were frozen in liquid nitrogen. Out of 89 H-MRS voxels, only 39 with a corresponding tissue specimen suitable for biochemical processing were included in the analysis. RNA was extracted from all the 39 samples and reverse-transcribed into cDNA. Choline kinase α and β gene expression as well as genes of the transmembrane transporters OCT1, OCT2, OCT3, CTL1, CTL3, CTL4 and CHT1 were studied using reverse transcriptase polymerase chain reaction. The expression level of each gene (ΔCt), was normalized referred to that of the RPL19 gene. The Spearman rank correlation coefficient was used to analyse variables. There was no overexpression of genes coding for kinases; however, significant correlation was observed between kinase α sub-type and the tCho peak (P=.002; r=0.51). OCT1 was the most overexpressed transporter gene. Less overexpressed CTL1 gene was significantly correlated with the tCho peak (P=.02; r=0.38). Choline transporters seem to play a predominant role in the increase in total choline concentration at the gene expression level in our model.
    Magnetic Resonance Imaging 04/2012; 30(7):1010-6. · 2.06 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The endoplasmic reticulum (ER) is the main site of protein and lipid synthesis, membrane biogenesis, xenobiotic detoxification and cellular calcium storage, and perturbation of ER homeostasis leads to stress and the activation of the unfolded protein response. Chronic activation of ER stress has been shown to have an important role in the development of insulin resistance and diabetes in obesity. However, the mechanisms that lead to chronic ER stress in a metabolic context in general, and in obesity in particular, are not understood. Here we comparatively examined the proteomic and lipidomic landscape of hepatic ER purified from lean and obese mice to explore the mechanisms of chronic ER stress in obesity. We found suppression of protein but stimulation of lipid synthesis in the obese ER without significant alterations in chaperone content. Alterations in ER fatty acid and lipid composition result in the inhibition of sarco/endoplasmic reticulum calcium ATPase (SERCA) activity and ER stress. Correcting the obesity-induced alteration of ER phospholipid composition or hepatic Serca over-expression in vivo both reduced chronic ER stress and improved glucose homeostasis. Hence, we established that abnormal lipid and calcium metabolism are important contributors to hepatic ER stress in obesity. (HEPATOLOGY 2011.
    Hepatology 12/2011; 54(6):2260-5. · 12.00 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The role of progenitor cells in liver repair and fibrosis has been extensively described, but their purification remains a challenge, hampering their characterization and use in regenerative medicine. To address this issue, we developed an easy and reproducible liver progenitor cell (LPC) isolation strategy based on aldehyde dehydrogenase (ALDH) activity, a common feature shared by many progenitor cells. We demonstrate that a subset of nonparenchymal mouse liver cells displays high levels of ALDH activity, allowing the isolation of these cells by fluorescence-activated cell sorting. Immunocytochemistry and qPCR analyses on freshly isolated ALDH(+) cells reveal an enrichment in cells expressing liver stem cell markers such as EpCAM, CK19, CD133, and Sox9. In culture, the ALDH(+) population can give rise to functional hepatocyte-like cells as illustrated by albumin and urea secretion and cytochrome P450 activity. ALDH1A1 expression can be detected in canals of Hering and bile duct epithelial cells and is increased on liver injury. Finally, we showed that the isolation and differentiation toward hepatocyte-like cells of LPCs with high ALDH activity is also successfully applicable to human liver samples. CONCLUSION: High ALDH activity is a feature of LPCs that can be taken advantage of to isolate these cells from untreated mouse as well as human liver tissues. This novel protocol is practically relevant, because it provides an easy and nontoxic method to isolate liver stem cells from normal tissue for potential therapeutic purposes.
    Hepatology 09/2011; 55(2):540-52. · 12.00 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: When hepatocyte proliferation is impaired, liver progenitor cells (LPC) are activated to participate in liver regeneration. We used the 2-acetaminofluorene/partial hepatectomy (AAF/PH) model to evaluate the contribution of LPC to liver cell replacement and function restoration. Fischer rats subjected to AAF/PH (or PH alone) were investigated 7, 10 and 14 days post-hepatectomy. Liver mass recovery (LMR) was estimated, and the liver mass to body weight ratio calculated. We used serum albumin and bilirubin levels, and liver albumin mRNA levels to assess the liver function. LPC expansion was analyzed by cytokeratin 19 (CK19), glutathione S-transferase protein (GSTp) immunohistochemistry and by CK19, CD133, transforming growth factor-β1 and hepatocyte growth factor mRNA expression in livers. Cell proliferation was evaluated by Ki67 and BrdU immunostaining. Compared with PH alone where LMR was ∼100% 14 days post-PH, LMR was defective in AAF/PH rats (64.1±15.5%, P=0.0004). LPC expansion was scarce in PH livers (0.5±0.4% of CK19(+) area), but significant in AAF/PH livers (8.5±7.2% of CK19(+)), and inversely correlated to LMR (r(2)=0.63, P<0.0001). A quarter of AAF/PH animals presented liver failure (low serum albumin and high serum bilirubin) 14 days post-PH. Compared with animals with preserved function, this was associated with a lower LMR (50±6.8 vs 74.6±9.4%, P=0.0005), a decreased liver to body weight ratio (2±0.3 vs 3.5±0.6%, P=0.001), and a larger LPC expansion such as proliferating Ki67(+) LPC covered 17.4±4.2% of the liver parenchyma vs 3.1±1.5%, (P<0.0001). Amongst those, rare LPC with an intermediate hepatocyte-like phenotype were seen. Also, less than 2% of hepatocytes were engaged into the cell cycle (Ki67(+)), while more numerous (∼25% of hepatocytes) in the livers with preserved function. These observations suggest that, in this model, the efficient recovery of the liver function was ensured rather by the proliferation of mature hepatocytes than by the LPC expansion and differentiation into hepatocytes.
    Laboratory Investigation 09/2011; 92(1):72-81. · 3.96 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aims: Apelin and its receptor have emerged as promising targets for the treatment of insulin resistance. Indeed, peripheral administration of apelin stimulates glucose utilization and insulin sensitivity via a nitric oxide (NO) pathway. In addition to being expressed on peripheral metabolically active adipose tissues, apelin is also found in the brain. However, no data are available on the role of central effects of apelin on metabolic control. We studied glucose metabolism in response to acute and chronic intracerebroventricular (i.c.v.) injection of apelin performed in normal and obese/diabetic mice. Results: We demonstrate that i.c.v. injection of apelin into fed mice improves glucose control via NO-dependent mechanisms. These results have been strengthened by transgenic (eNOS-KO mice), pharmacological (L-NMMA i.c.v. treated mice), and real-time measurement of NO release with amperometric probes detection. High-fat diet-fed mice displayed a severely blunted response to i.c.v. apelin associated with a lack of NO response by the hypothalamus. Moreover, central administration of high dose apelin in fasted normal mice provoked hyperinsulinemia, hyperglycemia, glucose intolerance, and insulin resistance. Conclusion: These data provide compelling evidence that central apelin participates in the regulation of glucose homeostasis and suggest a novel pathophysiological mechanism involved in the transition from normal to diabetic state.
    Antioxidants & Redox Signaling 09/2011; 15(6):1477-1496. · 8.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Activation of Ras and its downstream signaling pathways, likely contribute to the development of hepatocarcinoma. We have previously shown that intraperitoneal injections of the Ras inhibitor S-trans, trans-farnesylthiosalicyclic acid (FTS) blocks Ras activation and prevents heptocarcinoma development in rats receiving weekly injections of the carcinogene diethylnitrosamine (DEN) for 16 wk. Using this in vivo model, we evaluated the relationship between the tumor preventive effect of Ras inhibition and activation of downstream signaling pathways, cell proliferation, cell cycle events, and angiogenesis. Western blotting, quantitative PCR, immunohistochemistry, and transcription factor activity assays were used. DEN-induced activation of NFkB and Stat3 was abrogated by FTS treatment. FTS treatment showed no effect on DEN-induced elevation of TNFα, interleukin 6 and TLR4, known activators of these transcription factors. FTS significantly reduced phosphorylation of the MAPkinase p38 and of the p70S6 kinase, a surrogate marker for mTor activation, without affecting ERK and AKT phosphorylation. These events were associated with reduced c-myc and cyclin D expression as well as reduced cell proliferation in transformed, GSTp-positive hepatocytes. Moreover, FTS treatment shifted cell proliferation from transformed hepatocytes to apparently normal, GSTp negative hepatocytes. FTS treatment did not down-regulate expression of angiogenesis markers HIFα, VEGF, VEGF receptor1, and placenta growth factor. FTS treatment inhibits important signaling pathways involved in cellular proliferation leading to strongly reduced proliferation of transformed hepatocytes without affecting normal hepatocytes. This re-adjustment of the proliferation balance likely contributes to the tumor preventive of FTS in the context of Ras inhibition in hepatocarcinogenesis. © 2011 Wiley Periodicals, Inc.
    Molecular Carcinogenesis 08/2011; 51(10):816-25. · 4.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We aimed to evaluate activation of macrophages in insulin-sensitive tissues (liver, adipose tissue, and muscles) under high-fat diet (HFD) and elucidate the role of Kupffer cells (KC) in HFD-induced insulin resistance. Tissue macrophage populations, insulin signaling, and sensitivity were evaluated in mice fed a HFD for 4 or 16 wk. Selective KC depletion was obtained by intravenous injections of liposome-encapsulated clodronate. Mice fed a HFD for 4 to 16 wk have hepatic and peripheral insulin resistance together with macrophage recruitment in the adipose tissue but not in the liver. Depletion of KC for the last 10 d of the 16 wk experiment fails to improve insulin sensitivity compared to PBS-treated animals. In contrast, preventive KC depletion prior to and during the 4 wk HFD attenuates the development of obesity, adiposity, adipose tissue inflammation (P<0.01 vs. PBS group), and insulin resistance (P<0.01). Interestingly, in mice fed a normal diet, prolonged KC depletion ameliorates insulin sensitivity and decreases adiposity without altering physiological body weight gain or food intake. Preventive and prolonged KC depletion ameliorates insulin sensitivity and prevents adipose tissue inflammation, suggesting a communication between the liver and the adipose tissue in the development of HFD-induced metabolic alterations.
    The FASEB Journal 08/2011; 25(12):4301-11. · 5.70 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Activation of myofibroblasts (MF) and extracellular matrix (ECM) deposition predispose the expansion and differentiation of liver progenitor cells (LPC) during chronic liver injury. Because Kupffer cells (KC) are active modulators of tissue response and fibrosis, we analyzed their role in a model of LPC proliferation. A choline-deficient diet, supplemented by ethionine (CDE) was administrated to C57Bl/6J mice that were depleted of KC by repeated injections of clodronate (CLO) and compared to PBS-injected mice. On CDE, massive KC activation was observed in the PBS group, but this was blunted in CLO-treated mice. The depletion of KC did not influence LPC proliferation but reduced their invasive behavior. Instead of being found far into the parenchyma, as was found in the PBS group (mean distance from portal vein: 209 μm), LPC of CLO mice remained closer to the portal area (138 μm), forming aggregates and phenotypically resembling cells of biliary lineage. Notably, removal of KC was also associated with a significant decrease in amount of MF and ECM and in the expression of profibrotic factors. Thus, besides ECM and MF, KC are also a significant component of the microenvironmental changes preceding LPC expansion. Depletion of KC may limit the LPC parenchymal invasion through a deficiency in chemoattracting factors, reduced activation of MF, and/or a paucity of the ECM framework necessary for cell motility.
    American Journal Of Pathology 08/2011; 179(4):1839-50. · 4.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND& AIMS: Embryonic biliary precursor cells form a periportal sheet called the ductal plate, which is progressively remodeled to generate intrahepatic bile ducts. A limited number of ductal plate cells participate in duct formation; those not involved in duct development are believed to involute by apoptosis. Moreover, cells that express the SRY-related HMG box transcription factor 9 (SOX9), which include the embryonic ductal plate cells, were proposed to continuously supply the liver with hepatic cells. We investigated the role of the ductal plate in hepatic morphogenesis. Apoptosis and proliferation were investigated by immunostaining of mouse and human fetal liver tissue. The postnatal progeny of SOX9-expressing ductal plate cells was analyzed after genetic labeling, at the ductal plate stage, by Cre-mediated recombination of a ROSA26RYFP reporter allele. Inducible Cre expression was induced by SOX9 regulatory regions, inserted in a bacterial artificial chromosome. Livers were studied from mice under normal conditions and during diet-induced regeneration. Ductal plate cells did not undergo apoptosis and showed limited proliferation. They generated cholangiocytes lining interlobular bile ducts, bile ductules, and canals of Hering, as well as periportal hepatocytes. Oval cells that appeared during regeneration also derived from the ductal plate. We did not find that liver homeostasis required a continuous supply of cells from SOX9-expressing progenitors. The ductal plate gives rise to cholangiocytes lining the intrahepatic bile ducts, including its most proximal segments. It also generates periportal hepatocytes and adult hepatic progenitor cells.
    Gastroenterology 06/2011; 141(4):1432-8, 1438.e1-4. · 12.82 Impact Factor

Publication Stats

3k Citations
572.79 Total Impact Points

Institutions

  • 1996–2014
    • Catholic University of Louvain
      • • Institute of Experimental and Clinical Research (IREC)
      • • Laboratory of Hepatogastroenterology
      Walloon Region, Belgium
  • 2007–2008
    • Cliniques Universitaires Saint-Luc
      • Division of Gastroenterology
      Brussels, BRU, Belgium
  • 2003–2007
    • Westmead Millennium Institute
      Sydney, New South Wales, Australia
  • 2002
    • Westmead Millennium Institute
      Paramatta, New South Wales, Australia