The IRβ/HCF-1/ChREBP axis: A new paradigm in insulin-regulated hepatic lipogenesis

To determine whether insulin controls hepatic de novo lipogenesis (DNL) through an HCF-1-dependent modulation of ChREBP that is distinct from the canonical SREBP1c pathway.

AML-12 mouse hepatocytes were subjected to 10 μg/mL insulin and 25 mM glucose for 6 h. IRβ or HCF-1 was knocked down with lentiviral shRNA (≈80 % efficiency). Lipid droplets were quantified by Nile-Red staining; mRNA and protein levels were measured by RT-qPCR, Western blot, immunofluorescence and RNA-seq. Co-immunoprecipitation was used to test complex formation.

Insulin reduced lipid accumulation and suppressed ChREBP protein and its nuclear localization in AML-12 hepatocytes without altering SREBP1c. Knock-down of IRβ or HCF-1 abolished insulin-mediated ChREBP suppression, increased lipid droplets and up-regulated lipogenic genes. HCF-1 co-immunoprecipitated with IRβ, indicating formation of an insulin-responsive IRβ/HCF-1 complex that restrains ChREBP-driven lipogenesis.

We identify an IRβ/HCF-1/ChREBP regulatory node in hepatocytes that can repress lipogenic genes independently of SREBP1c. The axis constitutes a testable target for understanding selective insulin action on hepatic lipid metabolism and for future in-vivo studies of fatty-liver disease.