Unknown,Transcriptomics,Genomics,Proteomics

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Altered glycogen metabolism causes hepatomegaly following an Atg7 deletion

ABSTRACT: Autophagy is a lysosomal degradation process involved in the turnover of organelles or other cell constituents, in providing sources for energy production under starving conditions, and in cell metabolism. A key protein in the macroautophagic machinery is the autophagy related protein (Atg) 7. Constitutive deletion of Atg7 is lethal at birth. A conditional deletion of Atg7 in hepatocytes leads to hepatomegaly and in aged animals to liver tumors. With this study, we aimed at analyzing the hepatomegaly development more detailed. The 3- to 4-fold enlargement of the liver takes place between day 25 and 35 after birth (P25-P35) and persists at least until P90. This is accompanied by a change in the expression of enzymes involved in the glycogen/glucose metabolism. While glycogen synthesis is inhibited, glucose is preferentially kept as glucose-6-phosphate inside the cells, inducing a swelling of the cells caused by hyperosmolarity. An increase of lipogenic enzymes suggests that glucose-6-phosphate is delivered to lipogenic pathways, which is supported by the occurrence of a steatosis around P30. The development of hepatomegaly is accompanied by a polyploidisation of hepatocytes, an enhanced expression of genes related to inflammatory processes, and an infiltration of macrophages. Our data provide evidence that the attenuation of macroautophagy in hepatocytes leads to a glucose retention which causes cell swelling. The resulting hepatomegaly, which develops in a time interval of about 10 days, perturbs liver perfusion and induces an inflammatory reaction together with polyploidisation.

ORGANISM(S): Mus musculus

SUBMITTER: Chrysanti Skevaki

PROVIDER: E-MTAB-4389 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:abstract1: Glycogen storage disease type Ia (GSD Ia) is an inborn error of metabolism caused by defective glucose-6-phosphatase (G6PC) activity. GSD Ia patients exhibit severe hepatomegaly due to glycogen and triglyceride (TG) accumulation in the liver. We have previously shown that the activity of Carbohydrate Response Element Binding Protein (ChREBP), a key regulator of glycolysis and de novo lipogenesis, is increased in GSD Ia. In the current study we assessed the contribution of ChREBP to non-alcoholic fatty liver disease (NAFLD) development in a mouse model for hepatic GSD Ia. PMID : 32083759 Abstract2:Glycogen storage disease type 1a (GSD Ia) is an inborn error of metabolism caused by a defect in glucose-6-phosphatase (G6PC) activity, which induces severe hepatomegaly and increases the risk for liver cancer in patients. Hepatic GSD Ia is characterized by constitutive activation of Carbohydrate Response Element Binding Protein (ChREBP), a glucose-sensitive transcription factor that has been proposed as a pro-oncogenic molecular switch that supports tumour progression. Here we studied the contribution of ChREBP signalling on liver disease progression and tumour susceptibility in a mouse model for GSD Ia. Hepatocyte-specific G6pc knockout (L-G6pc-/-) mice were treated with AAV-shChREBP to normalize hepatic ChREBP activity. Hepatic ChREBP normalization induced dysplastic liver growth, massively increased hepatocyte size and sensitized to hepatic inflammation and liver fibrosis in GSD Ia mice. Furthermore, the nuclear levels of the oncoprotein YAP were increased and its transcriptional targets were induced in ChREBP normalized GSD Ia mice. Hepatic ChREBP normalization furthermore induced DNA damage and mitotic activity in GSD Ia mice, while chromosomal instability, cGAS-STING pathway, senescence, and hepatocyte dedifferentiation gene signatures emerged. Upon ChREBP silencing in immortalized human hepatocytes, on the other hand, the induction of YAP target gene expression was paralleled by cell cycle arrest, cell death, and reduced proliferation. In conclusion, our findings indicate that ChREBP activity limits hepatomegaly while protecting against liver disease progression and hepatocellular tumour induction in GSD Ia. These results underline the importance to establish the context-specific roles of ChREBP to define its therapeutic potential. PMID:37085901

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Altered glycogen metabolism causes hepatomegaly following an Atg7 deletion

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