Characterization of the involvement of nutrient sensor mTORC1 in the hepatic steatosis, steatohepatitis, and hepatocarcinoma induced by PTEN deletion into hepatocytes

Abstract

Non-alcoholic fatty liver disease (NAFLD) comprises a group of diseases characterized by exacerbated hepatic liver accumulation progressively varying from a simple steatosis (NAFL) to more serious steatopatite (NASH) and hepatocellular carcinoma (HCC). Several studies have found that the canonical growth factors intracellular PI3K-mTORC2-Akt-mTORC1 signaling pathway actively participates, by mechanisms not yet completely defined, in the development of NAFL-NASH-HCC progression. One of the difficulties, though, in the characterization of mTORC1 specific actions in this progression results from its intense cross-talk with mTORC2. Indeed, mTORC2 is a positive upstream regulator of mTORC1 that, in turn, inhibits mTORC2 activity through a negative feedback on IRS function. To overcome this problem, we propose herein to study the NAFL-NASH-HCC progression in mice with a combined deletion of Raptor (mTORC1 deficiency) and Pten exclusively in hepatocytes. As Pten is positioned downstream to IRS, its deletion promotes the constitutive activation of mTORC2-Akt-mTORC1 pathway without interfering with the negative feedback exerted by mTORC1 on IRS function. For this, mice with deletion of either Pten, or Raptor or both Raptor and Pten exclusively in hepatocytes will be evaluated for glucose (glucose and insulin tolerances) and lipid metabolism (lipogenesis, lipolysis, fatty acid oxidation and TAG secretion), liver and serum lipid profile (lipidomics), mitochondrial and peroxisome contents and function, oxidative stress, resident leukocytes by FACS, intracellular insulin and proinflammatory signaling, gene expression profile, and inflammatory cytokines.