Abstract
Thyroid hormone (TH) action is essential for hepatic lipid synthesis and oxidation. Analysis of hepatocyte-specific thyroid receptor β1 (TRβ1) knockout mice confirmed a role for TH in stimulating de novo lipogenesis and fatty acid oxidation through its nuclear receptor. Specifically, TRβ1 and its principal corepressor NCoR1 in hepatocytes repressed de novo lipogenesis, whereas the TH-mediated induction of lipogenic genes depended on the transcription factor ChREBP. Mice with a hepatocyte-specific deficiency in ChREBP lost TH-mediated stimulation of the lipogenic program, which, in turn, impaired the regulation of fatty acid oxidation. TH regulated ChREBP activation and recruitment to DNA, revealing a mechanism by which TH regulates specific signaling pathways. Regulation of the lipogenic pathway by TH through ChREBP was conserved in hepatocytes derived from human induced pluripotent stem cells. These results demonstrate that TH signaling in the liver acts simultaneously to enhance both lipogenesis and fatty acid oxidation.