at the CNIC

Tag: PPARα

Limited survival and impaired hepatic fasting metabolism in mice with constitutive Rag GTPase signaling

Celia de la Calle Arregui, Ana Belén Plata-Gómez, Nerea Deleyto-Seldas, Fernando García, Ana Ortega-Molina, Julio Abril-Garrido, Elena Rodriguez, Ivan Nemazanyy, Laura Tribouillard, Alba de Martino, Eduardo Caleiras, Ramón Campos-Olivas, Francisca Mulero, Mathieu Laplante, Javier Muñoz, Mario Pende, Guadalupe Sabio, David M. Sabatini & Alejo Efeyan.

The mechanistic target of rapamycin complex 1 (mTORC1) integrates cellular nutrient signaling and hormonal cues to control metabolism. We have previously shown that constitutive nutrient signaling to mTORC1 by means of genetic activation of RagA (expression of GTP-locked RagA, or RagAGTP) in mice resulted in a fatal energetic crisis at birth.

mTORC1 in adaptation to fasting.
mTORC1 in adaptation to fasting.

Herein, we rescue neonatal lethality in RagAGTP mice and find morphometric and metabolic alterations that span glucose, lipid, ketone, bile acid and amino acid homeostasis in adults, and a median lifespan of nine months. Proteomic and metabolomic analyses of livers from RagAGTP mice reveal a failed metabolic adaptation to fasting due to a global impairment in PPARα transcriptional program. These metabolic defects are partially recapitulated by restricting activation of RagA to hepatocytes, and revert by pharmacological inhibition of mTORC1. Constitutive hepatic nutrient signaling does not cause hepatocellular damage and carcinomas, unlike genetic activation of growth factor signaling upstream of mTORC1.

In summary, RagA signaling dictates dynamic responses to feeding-fasting cycles to tune metabolism so as to match the nutritional state.

JNK-mediated disruption of bile acid homeostasis promotes intrahepatic cholangiocarcinoma

Elisa Manieri, Cintia Folgueira, María Elena Rodríguez, Luis Leiva-Vega, Laura Esteban-Lafuente, Chaobo Chen, Francisco Javier Cubero, Tamera Barrett, Julie Cavanagh-Kyros, Davide Seruggia, Alejandro Rosell, Fátima Sanchez-Cabo, Manuel Jose Gómez, Maria J. Monte, Jose J. G. Marin, Roger J. Davis, Alfonso Mora & Guadalupe Sabio.

Obesity is associated with hepatic steatosis and activation of the cJun NH2-terminal kinase (JNK) stress-signaling pathway. Studies in mice demonstrate that JNK deficiency in the liver prevents the development of hepatic steatosis. This observation suggests that inhibition of JNK signaling may represent a possible treatment for hepatic steatosis. However, the long-term consequences of JNK inhibition are poorly understood.

Liver cholangiocarcinoma (Photo: Chaobo Chen).

Here we demonstrate that loss of JNK causes changes in cholesterol and bile acid metabolism that promote cholestasis, bile duct proliferation, and intrahepatic cholangiocarcinoma. We identify PPARα activation as the molecular mechanism that accounts for this phenotype .

Our analysis has important implications for the long-term use of JNK inhibitors for the treatment of obesity.

© 2021 Sabio lab

Theme by Anders NorénUp ↑