title: Hepatocyte-specific Keap1 deletion reduces liver steatosis but not inflammation during non-alcoholic steatohepatitis development.
abstract: Generation of reactive oxygen species (ROS) in response to fatty acids accumulation has been classically proposed as a possible "second hit" triggering progression from simple steatosis to non-alcoholic steatohepatitis (NASH). In this study we challenged hepatocyte-specific Keap1 knockout mice (Keap1(Δhepa)) and littermate Cre- controls (Keap1(fx/fx)) with two different diet models of NASH in order to evaluate the effects of the anti-oxidant transcription factor Nrf2 over-activation on hepatic metabolism and disease progression. After 4 weeks of MCD diet the liver/body weight ratio of Keap1(Δhepa) mice was significantly higher compared to littermate controls with no differences in total body weight. Strikingly, liver histology revealed a dramatic reduction of lipid droplets confirmed by a decreased content of intra-hepatic triglycerides in Keap1(Δhepa) compared to controls. In parallel to reduced expression of genes involved in lipid droplet formation, protein expression of Liver X Receptor (LXRα/β) and Peroxisome proliferator-activated receptor α (PPARα) was significantly decreased. In contrast, genes involved in mitochondrial lipid catabolism were markedly up-regulated in Keap1(Δhepa) livers. A similar phenotype characterized by inhibition of lipogenesis in favor of increased mitochondrial catabolic activity was also observed after 13 weeks of western diet administration. MCD-induced apoptosis was significantly dampened in Keap1(Δhepa) compared to Keap1(fx/fx) as detected by TUNEL, cleaved caspase-3 and Bcl-2 protein expression analyses. However, no differences in inflammatory F4/80- and CD11b-positive cells and pro-fibrogenic genes were detected between the two groups. Although hepatic lack of Keap1 did not ameliorate inflammation, the resulting constitutive Nrf2 over-activation in hepatocytes strongly reduced hepatic steatosis via enhanced lipid catabolism and repressed de novo lipogenesis during murine NASH development.
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany. Electronic address: pramadori@ukaachen.de.
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Ramadori
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Drescher
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Erschfeld
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Schumacher
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Cordula
authors.initials: C
authors.lastname: Berger
authors.affiliation: Institute of Anatomy and Cell Biology, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Athanassios
authors.initials: A
authors.lastname: Fragoulis
authors.affiliation: Institute of Anatomy and Cell Biology, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Schenkel
authors.affiliation: Department of Pharmacology & Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Kensler
authors.affiliation: Institute of Anatomy and Cell Biology, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Wruck
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Trautwein
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Daniela C
authors.initials: DC
authors.lastname: Kroy
authors.affiliation: Department of Medicine III, RWTH Aachen University Hospital, Aachen, Germany. Electronic address: kstreetz@ukaachen.de.
authors.forename: Konrad L
authors.initials: KL
authors.lastname: Streetz
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D002784:Cholesterol / Q000097:blood; D022781:Hepatocytes / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1 / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D065626:Non-alcoholic Fatty Liver Disease / Q000097:blood / Q000235:genetics* / Q000276:immunology; D009929:Organ Size; D010084:Oxidation-Reduction
chemical_list: C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D002784:Cholesterol
keywords: Bcl-2; LXRα/β; Lipid metabolism; Nrf2; Oxidative stress