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Novel defatting strategies reduce lipid accumulation in primary human culture models of liver steatosis.

ABSTRACT: Normothermic perfusion provides a means to rescue steatotic liver grafts, including by pharmacological defatting. In this study, we tested the potential of new drug combinations to trigger defatting in three human culture models, primary hepatocytes with induced steatosis, primary hepatocytes isolated from steatotic liver, and precision-cut liver slices (PCLS) of steatotic liver. Forskolin, L-carnitine and a PPAR? agonist were all combined with rapamycin, an immunosuppressant that induces autophagy, in a D-FAT cocktail. D-FAT was tested alone or in combination with necrosulfonamide, an inhibitor of mixed lineage kinase domain like pseudokinase involved in necroptosis. Within 24?h, in all three models, D-FAT induced a decrease in triglyceride content by 30%, attributable to an upregulation of genes involved in free fatty acid ?-oxidation and autophagy, and a downregulation of those involved in lipogenesis. Defatting was accompanied by a decrease in endoplasmic reticulum stress and in the production of reactive oxygen species. The addition of necrosulfonamide increased the efficacy of defatting by 8%-12% in PCLS, with a trend towards increased autophagy. In conclusion, culture models, notably PCLS, are insightful to design strategies for liver graft rescue. Defatting can be rapidly achieved by combinations of drugs targeting mitochondrial oxidative metabolism, macro-autophagy and lipogenesis.

SUBMITTER: Aoudjehane L

PROVIDER: S-EPMC7197711 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Novel defatting strategies reduce lipid accumulation in primary human culture models of liver steatosis.

Aoudjehane Lynda L Gautheron Jérémie J Le Goff Wilfried W Goumard Claire C Gilaizeau Julia J Nget Chan Sonavine CS Savier Eric E Atif Muhammad M Lesnik Philippe P Morichon Romain R Chrétien Yves Y Calmus Yvon Y Scatton Olivier O Housset Chantal C Conti Filomena F

Disease models & mechanisms 20200429 4

Normothermic perfusion provides a means to rescue steatotic liver grafts, including by pharmacological defatting. In this study, we tested the potential of new drug combinations to trigger defatting in three human culture models, primary hepatocytes with induced steatosis, primary hepatocytes isolated from steatotic liver, and precision-cut liver slices (PCLS) of steatotic liver. Forskolin, L-carnitine and a PPARα agonist were all combined with rapamycin, an immunosuppressant that induces autoph ...[more]

PMID: 32094147

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Project description:Strategies to increase the use of steatotic donor livers are required to tackle the mortality on the transplant waiting list. We aimed to test the efficacy of pharmacological enhancement of the lipid metabolism of human livers during ex situ normothermic machine perfusion to promote defatting and improve the functional recovery of the organs. Because of steatosis, 10 livers were discarded and were allocated either to a defatting group that had the perfusate supplemented with a combination of drugs to enhance lipid metabolism or to a control group that received perfusion fluid with vehicle only. Steatosis was assessed using tissue homogenate and histological analyses. Markers for lipid oxidation and solubilization, oxidative injury, inflammation, and biliary function were evaluated by enzyme-linked immunosorbent assay, immunohistochemistry, and in-gel protein detection. Treatment reduced tissue triglycerides by 38% and macrovesicular steatosis by 40% over 6 hours. This effect was driven by increased solubility of the triglycerides (P = 0.04), and mitochondrial oxidation as assessed by increased ketogenesis (P = 0.008) and adenosine triphosphate synthesis (P = 0.01) were associated with increased levels of the enzymes acyl-coenzyme A oxidase 1, carnitine palmitoyltransferase 1A, and acetyl-coenzyme A synthetase. Concomitantly, defatted livers exhibited enhanced metabolic functional parameters such as urea production (P = 0.03), lower vascular resistance, lower release of alanine aminotransferase (P = 0.049), and higher bile production (P = 0.008) with a higher bile pH (P = 0.03). The treatment down-regulated the expression of markers for oxidative injury as well as activation of immune cells (CD14; CD11b) and reduced the release of inflammatory cytokines in the perfusate (tumor necrosis factor α; interleukin 1β). In conclusion, pharmacological enhancement of intracellular lipid metabolism during normothermic machine perfusion decreased the lipid content of human livers within 6 hours. It also improved the intracellular metabolic support to the organs, leading to successful functional recovery and decreased expression of markers of reperfusion injury.

Project description:Abstract: Non-alcoholic steatohepatitis (NASH) is associated with a disturbed metabolism in liver and excessive accumulation of ectopic fat. Branched-chain amino acids (BCAAs) may beneficially modulate hepatic lipids, however it remains unclear whether individual BCAAs can attenuate already established NASH and oxidative-inflammatory stress associated with it. Therefore, mice were first put on a run-in fast food diet (FFD) for 26 weeks, these obese mice were then treated with individual BCAAs valine or isoleucine (3% of FFD) for another 12 weeks and compared to FFD controls. Valine and isoleucine treatment did not affect obesity, dyslipidemia, gut permeability or fecal fatty acid excretion, although significantly reduced hyperinsulinemia compared with FFD. Valine and isoleucine significantly reduced ALT, CK-18M30, and liver steatosis with a particularly pronounced effect on the microvesicular component (-61% by valine and -71% by isoleucine). Hepatic 4-hydroxynonenal (4-HNE) immunoreactivity, a marker for oxidative stress-induced lipid peroxidation, was also significantly decreased. Functional genomics analysis demonstrated that valine and isoleucine upregulated BCAA metabolism, deactivated master regulators of anabolic pathways related to steatosis (e.g. SREBPF1) and activated master regulators of mitochondrial biogenesis (e.g. PPARGC1a) and lipid catabolism (e.g. ACOX1, AMPK). The correction of critical metabolic pathways by valine and isoleucine was accompanied by a significant decrease of liver inflammation, and suppression of many FFD-stimulated cytokine and chemokine pathways including IL-1β, TNFα and CCR2 signaling. In conclusion, the dietary intervention with either valine or isoleucine corrected multiple metabolic processes in liver and reduced steatosis and inflammation with profound effects on oxidative stress and inflammatory pathways. Methods: Putative antifibrotic effects of butyrate were studied in Ldlr-/-.Leiden mice fed an obesogenic NASH-inducing diet (HFD) containing 2.5% (w/w) butyrate for 38 weeks and compared to an HFD control group. Antifibrotic mechanisms of butyrate were further investigated in TGF-β-stimulated primary human hepatic stellate cells (HSC). Results: HFD-fed mice developed obesity, insulin resistance, increased levels of plasma leptin, adipose tissue inflammation, gut permeability, dysbiosis and NASH-associated fibrosis. Butyrate corrected hyperinsulinemia, lowered plasma leptin levels and attenuated adipose tissue inflammation, without affecting gut permeability or microbiota composition. Butyrate lowered plasma ALT and CK-18M30 and attenuated hepatic steatosis and inflammation. Butyrate inhibited fibrosis development as demonstrated by decreased hepatic collagen content and Sirius-red-positive area. In TGF-β-stimulated HSC, butyrate dose-dependently reduced collagen deposition and decreased procollagen1α1 and PAI-1 protein expression. Transcriptomic analysis and subsequent pathway and upstream regulator analysis revealed deactivation of specific non-canonical TGF-β signaling pathways RhoA/Rock and PI3K/AKT and other important pro-fibrotic regulators (e.g. YAP/TAZ and MYC) by butyrate, providing a potential rationale for its antifibrotic effects. Conclusions: Butyrate protects against the development of obesity and insulin resistance-associated NASH and liver fibrosis. These antifibrotic effects are at least in part attributable to a direct effect on collagen production in hepatic stellate cells, as a result of inhibiting non-canonical TGF-β signaling.

Project description:Chronic alcohol causes hepatic steatosis and liver hypoxia. Hypoxia-regulated hypoxia-inducible factor 1-?, (HIF-1?) may regulate liporegulatory genes, but the relationship of HIF-1 to steatosis remains unknown. We investigated HIF-1? in alcohol-induced hepatic lipid accumulation. Alcohol administration resulted in steatosis, increased liver triglyceride levels, and increased serum alanine aminotransferase (ALT) levels, suggesting liver injury in wild-type (WT) mice. There was increased hepatic HIF-1? messenger RNA (mRNA), protein, and DNA-binding activity in alcohol-fed mice compared with controls. Mice engineered with hepatocyte-specific HIF-1 activation (HIF1dPA) had increased HIF-1? mRNA, protein, and DNA-binding activity, and alcohol feeding in HIF1dPA mice increased hepatomegaly and hepatic triglyceride compared with WT mice. In contrast, hepatocyte-specific deletion of HIF-1? [HIF-1?(Hep(-/-) )], protected mice from alcohol- and lipopolysaccharide (LPS)-induced liver damage, serum ALT elevation, hepatomegaly, and lipid accumulation. HIF-1?(Hep(-/-) ), WT, and HIF1dPA mice had equally suppressed levels of peroxisome proliferator-activated receptor ? mRNA after chronic ethanol, whereas the HIF target, adipocyte differentiation-related protein, was up-regulated in WT mice but not HIF-1?(Hep(-/-) ) ethanol-fed/LPS-challenged mice. The chemokine monocyte chemoattractant protein-1 (MCP-1) was cooperatively induced by alcohol feeding and LPS in WT but not HIF-1?(Hep(-/-) ) mice. Using Huh7 hepatoma cells in vitro, we found that MCP-1 treatment induced lipid accumulation and increased HIF-1? protein expression as well as DNA-binding activity. Small interfering RNA inhibition of HIF-1? prevented MCP-1-induced lipid accumulation, suggesting a mechanistic role for HIF-1? in hepatocyte lipid accumulation.Alcohol feeding results in lipid accumulation in hepatocytes involving HIF-1? activation. The alcohol-induced chemokine MCP-1 triggers lipid accumulation in hepatocytes via HIF-1? activation, suggesting a mechanistic link between inflammation and hepatic steatosis in alcoholic liver disease.

Project description:Persistent presence of perfluoroalkyl acids (PFAAs) in the environment is due to their extensive use in industrial and consumer products, and their slow decay. Biochemical tests in rodent demonstrated that these chemicals are potent modifiers of lipid metabolism and cause hepatocellular steatosis. However, the molecular mechanism of PFAAs interference with lipid metabolism remains to be elucidated. Currently, two major hypotheses are that PFAAs interfere with mitochondrial beta-oxidation of fatty acids and/or they affect the transcriptional activity of peroxisome proliferator-activated receptor ? (PPAR?) in liver. To determine the ability of structurally-diverse PFAAs to cause steatosis, as well as to understand the underlying molecular mechanisms, wild-type (WT) and PPAR?-null mice were treated with perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), or perfluorohexane sulfonate (PFHxS), by oral gavage for 7days, and their effects were compared to that of PPAR? agonist WY-14643 (WY), which does not cause steatosis. Increases in liver weight and cell size, and decreases in DNA content per mg of liver, were observed for all compounds in WT mice, and were also seen in PPAR?-null mice for PFOA, PFNA, and PFHxS, but not for WY. In Oil Red O stained sections, WT liver showed increased lipid accumulation in all treatment groups, whereas in PPAR?-null livers, accumulation was observed after PFNA and PFHxS treatment, adding to the burden of steatosis observed in control (untreated) PPAR?-null mice. Liver triglyceride (TG) levels were elevated in WT mice by all PFAAs and in PPAR?-null mice only by PFNA. In vitro ?-oxidation of palmitoyl carnitine by isolated rat liver mitochondria was not inhibited by any of the 7 PFAAs tested. Likewise, neither PFOA nor PFOS inhibited palmitate oxidation by HepG2/C3A human liver cell cultures. Microarray analysis of livers from PFAAs-treated mice indicated that the PFAAs induce the expression of the lipid catabolism genes, as well as those involved in fatty acid and triglyceride synthesis, in WT mice and, to a lesser extent, in PPAR?-null mice. These results indicate that most of the PFAAs increase liver TG load and promote steatosis in mice We hypothesize that PFAAs increase steatosis because the balance of fatty acid accumulation/synthesis and oxidation is disrupted to favor accumulation.

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Novel defatting strategies reduce lipid accumulation in primary human culture models of liver steatosis.

Publications

Novel defatting strategies reduce lipid accumulation in primary human culture models of liver steatosis.

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