Circadian clocks control several homeostatic processes in mammals through internal molecular mechanisms. Chronic perturbation of circadian rhythms is associated with metabolic diseases and increased cancer risk, including liver cancer.
The hepatic physiology follows a daily rhythm, driven by clock genes that control the expression of several proteins involved in distinct metabolic pathways. Alteration of the liver clock results in metabolic disorders, such as non-alcoholic fatty liver diseases (NAFLD) and impaired glucose metabolism, that can trigger the activation of oncogenic pathways, inducing spontaneous hepatocarcinoma (HCC).
In this review, we provide an overview of the role of the liver clock in the metabolic and oncogenic changes that lead to HCC and discuss new potentially useful targets for prevention and management of HCC.
Guadalupe Sabio explica para El Diario.es que durante sus últimos años de trabajo han descubierto que el tejido adiposo sufre una transformación en la obesidad. En esa transformación se activan proteínas del estrés que pueden provocar que se desarrollen distintas enfermedades.
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.
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.