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Hepatocyte specific expression of an oncogenic variant of ?-catenin results in lethal metabolic dysfunction in mice.

ABSTRACT: Wnt/?-catenin signaling plays a crucial role in embryogenesis, tissue homeostasis, metabolism and malignant transformation of different organs including the liver. Continuous ?-catenin signaling due to somatic mutations in exon 3 of the Ctnnb1 gene is associated with different liver diseases including cancer and cholestasis.Expression of a degradation resistant form of ?-catenin in hepatocytes resulted in 100% mortality within 31 days after birth. Ctnnb1CAhep mice were characterized by reduced body weight, significantly enlarged livers with hepatocellular fat accumulation around central veins and increased hepatic triglyceride content. Proteomics analysis using whole liver tissue revealed significant deregulation of proteins involved in fat, glucose and mitochondrial energy metabolism, which was also reflected in morphological anomalies of hepatocellular mitochondria. Key enzymes involved in transport and synthesis of fatty acids and cholesterol were significantly deregulated in livers of Ctnnb1CAhep mice. Furthermore, carbohydrate metabolism was substantially disturbed in mutant mice.Continuous ?-catenin signaling in hepatocytes results in premature death due to severe disturbances of liver associated metabolic pathways and mitochondrial dysfunction.To investigate the influence of permanent ?-catenin signaling on liver biology we analyzed mice with hepatocyte specific expression of a dominant stable form of ?-catenin (Ctnnb1CAhep ) and their WT littermates by serum biochemistry, histology, electron microscopy, mRNA profiling and proteomic analysis of the liver.

SUBMITTER: Lemberger UJ

PROVIDER: S-EPMC5834276 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Hepatocyte specific expression of an oncogenic variant of β-catenin results in lethal metabolic dysfunction in mice.

Lemberger Ursula J UJ Fuchs Claudia D CD Schöfer Christian C Bileck Andrea A Gerner Christopher C Stojakovic Tatjana T Taketo Makoto M MM Trauner Michael M Egger Gerda G Österreicher Christoph H CH

Oncotarget 20180130 13

<h4>Background</h4>Wnt/β-catenin signaling plays a crucial role in embryogenesis, tissue homeostasis, metabolism and malignant transformation of different organs including the liver. Continuous β-catenin signaling due to somatic mutations in exon 3 of the <i>Ctnnb1</i> gene is associated with different liver diseases including cancer and cholestasis.<h4>Results</h4>Expression of a degradation resistant form of β-catenin in hepatocytes resulted in 100% mortality within 31 days after birth. <i>Ctn ...[more]

PMID: 29541410

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Project description:Alterations in the energy homeostasis contribute to sepsis-mediated multiple organ failure. The liver plays a central role in metabolism and participates to the innate immune and inflammatory responses of sepsis. Several clinical and experimental studies have suggested that females are less susceptible to the adverse outcome of sepsis. However, underlying mechanisms of organ damage in sepsis remain largely undefined. AMP-activated protein kinase (AMPK) is an important regulator of mitochondrial quality control. The AMPK catalytic ?1 isoform is abundantly expressed in the liver. Here, we determined the role of hepatocyte AMPK?1 in sepsis by using hepatocyte-specific AMPK?1 knockout mice (H-AMPK?1 KO) generated with Cre-recombinase expression under the control of the albumin promoter. Using a clinically relevant model of polymicrobial sepsis by cecal ligation and puncture (CLP), we observed that male H-AMPK?1 KO mice had higher plasma levels of tumor necrosis factor-? and interleukin-6 and exhibited a more severe liver and lung injury than male H-AMPK?1 WT mice, as evaluated by histology and neutrophil infiltration at 18 h after CLP. Plasma levels of interleukin-10 and the keratinocyte-derived chemokine were similarly elevated in both KO and WT male mice. At transmission electron microscopy analysis, male H-AMPK?1 KO mice exhibited higher liver mitochondrial damage, which was associated with a significant decrease in liver ATP levels when compared to WT mice at 18 h after sepsis. Mortality rate was significantly higher in the male H-AMPK?1 KO group (91%) when compared to WT mice (60%) at 7 days after CLP. Female H-AMPK?1 WT mice exhibited a similar degree of histological liver and lung injury, but significantly milder liver mitochondrial damage and higher autophagy when compared to male WT mice after CLP. Interestingly, H-AMPK?1 KO female mice had lower organ neutrophil infiltration, lower liver mitochondrial damage and lower levels of cytokines than WT female mice. There was no significant difference in survival rate between WT and KO mice in the female group. In conclusion, our study demonstrates that AMPK?1 is a crucial hepatoprotective enzyme during sepsis. Furthermore, our results suggest that AMPK-dependent liver metabolic functions may influence the susceptibility to multiple organ injury in a sex-dependent manner.

Project description:Background & aimsPorphyrias result from anomalies of heme biosynthetic enzymes and can lead to cirrhosis and hepatocellular cancer. In mice, these diseases can be modeled by administration of a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), which causes accumulation of porphyrin intermediates, resulting in hepatobiliary injury. Wnt/β-catenin signaling has been shown to be a modulatable target in models of biliary injury; thus, we investigated its role in DDC-driven injury.Methodsβ-Catenin (Ctnnb1) knockout (KO) mice, Wnt co-receptor KO mice, and littermate controls were fed a DDC diet for 2 weeks. β-Catenin was exogenously inhibited in hepatocytes by administering β-catenin dicer-substrate RNA (DsiRNA), conjugated to a lipid nanoparticle, to mice after DDC diet and then weekly for 4 weeks. In all experiments, serum and livers were collected; livers were analyzed by histology, western blotting, and real-time PCR. Porphyrin was measured by fluorescence, quantification of polarized light images, and liquid chromatography-mass spectrometry.ResultsDDC-fed mice lacking β-catenin or Wnt signaling had decreased liver injury compared to controls. Exogenous mice that underwent β-catenin suppression by DsiRNA during DDC feeding also showed less injury compared to control mice receiving lipid nanoparticles. Control livers contained extensive porphyrin deposits which were largely absent in mice lacking β-catenin signaling. Notably, we identified a network of key heme biosynthesis enzymes that are suppressed in the absence of β-catenin, preventing accumulation of toxic protoporphyrins. Additionally, mice lacking β-catenin exhibited fewer protein aggregates, improved proteasomal activity, and reduced induction of autophagy, all contributing to protection from injury.Conclusionsβ-Catenin inhibition, through its pleiotropic effects on metabolism, cell stress, and autophagy, represents a novel therapeutic approach for patients with porphyria.Lay summaryPorphyrias are disorders resulting from abnormalities in the steps that lead to heme production, which cause build-up of toxic by-products called porphyrins. Liver is commonly either a source or a target of excess porphyrins, and complications can range from minor abnormalities to liver failure. In this report, we inhibited Wnt/β-catenin signaling in an experimental model of porphyria, which resulted in decreased liver injury. Targeting β-catenin affected multiple components of the heme biosynthesis pathway, thus preventing build-up of porphyrin intermediates. Our study suggests that drugs inhibiting β-catenin activity could reduce the amount of porphyrin accumulation and help alleviate symptoms in patients with porphyria.

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Hepatocyte specific expression of an oncogenic variant of ?-catenin results in lethal metabolic dysfunction in mice.

Publications

Hepatocyte specific expression of an oncogenic variant of β-catenin results in lethal metabolic dysfunction in mice.

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