Salt-inducible kinase 2 links transcriptional coactivator p300 phosphorylation to the prevention of ChREBP-dependent hepatic steatosis in mice
Julien Bricambert, … , Catherine Postic, Renaud Dentin
Julien Bricambert, … , Catherine Postic, Renaud Dentin
Published November 15, 2010
Citation Information: J Clin Invest. 2010;120(12):4316-4331. https://doi.org/10.1172/JCI41624.
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Research Article Metabolism

Salt-inducible kinase 2 links transcriptional coactivator p300 phosphorylation to the prevention of ChREBP-dependent hepatic steatosis in mice

Abstract

Obesity and type 2 diabetes are associated with increased lipogenesis in the liver. This results in fat accumulation in hepatocytes, a condition known as hepatic steatosis, which is a form of nonalcoholic fatty liver disease (NAFLD), the most common cause of liver dysfunction in the United States. Carbohydrate-responsive element–binding protein (ChREBP), a transcriptional activator of glycolytic and lipogenic genes, has emerged as a major player in the development of hepatic steatosis in mice. However, the molecular mechanisms enhancing its transcriptional activity remain largely unknown. In this study, we have identified the histone acetyltransferase (HAT) coactivator p300 and serine/threonine kinase salt-inducible kinase 2 (SIK2) as key upstream regulators of ChREBP activity. In cultured mouse hepatocytes, we showed that glucose-activated p300 acetylated ChREBP on Lys672 and increased its transcriptional activity by enhancing its recruitment to its target gene promoters. SIK2 inhibited p300 HAT activity by direct phosphorylation on Ser89, which in turn decreased ChREBP-mediated lipogenesis in hepatocytes and mice overexpressing SIK2. Moreover, both liver-specific SIK2 knockdown and p300 overexpression resulted in hepatic steatosis, insulin resistance, and inflammation, phenotypes reversed by SIK2/p300 co-overexpression. Finally, in mouse models of type 2 diabetes and obesity, low SIK2 activity was associated with increased p300 HAT activity, ChREBP hyperacetylation, and hepatic steatosis. Our findings suggest that inhibition of hepatic p300 activity may be beneficial for treating hepatic steatosis in obesity and type 2 diabetes and identify SIK2 activators and specific p300 inhibitors as potential targets for pharmaceutical intervention.

Authors

Julien Bricambert, Jonatan Miranda, Fadila Benhamed, Jean Girard, Catherine Postic, Renaud Dentin

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Figure 1

Hepatic SIK2 silencing impairs lipid homeostasis.

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Hepatic SIK2 silencing impairs lipid homeostasis. Mice were injected wit...
Mice were injected with unspecific (USi) or SIK2 shRNA adenovirus (SIK2i) and were studied 7 days later in the fed state. (A) Western blot analysis of key transcription factors and coactivators involved in the regulation of gluconeogenesis and lipogenesis in liver (n = 3–4 per group). (B) SIK2i mice develop hepatic steatosis as shown by increased liver size and H&E and oil red O staining of liver sections and by the rate of lipogenesis. Original magnification, ×200 (n = 4–8 per group; *P < 0.05). (C) Plasma glucose and insulin levels (n = 8 per group; *P < 0.01). (D) OGTT and ITT (n = 6 per group; *P < 0.01). (E and F) Total liver and plasma TGs and FFA levels (n = 8 per group; *P < 0.01). (G) Relative expression of glycolytic, lipogenic, and gluconeogenic genes (n = 8 per group; *P < 0.01). (H) Acetyl-CoA concentrations (n = 8 per group; *P < 0.02) and amounts of acetylated (Ac) H3K9, H4K8, and tubulin determined by Western blot analysis (n = 4 per group). (I) ChREBP, RNA polymerase II (RNA pol II) recruitment, and levels of acetylated H3K9 at the ChoRE-containing region of the L-PK promoter were measured by ChIP studies. The amount of immunoprecipitated H3 at the DNA was unchanged upon SIK2 silencing and was used as control to normalize H3K9 acetylation levels at the L-PK promoter (n = 8 per group; *P < 0.05). Data represent mean ± SEM.