Class IIa Histone Deacetylases Are Hormone-Activated Regulators of FOXO and Mammalian Glucose Homeostasis

Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA.
Cell (Impact Factor: 32.24). 05/2011; 145(4):607-21. DOI: 10.1016/j.cell.2011.03.043
Source: PubMed


Class IIa histone deacetylases (HDACs) are signal-dependent modulators of transcription with established roles in muscle differentiation and neuronal survival. We show here that in liver, class IIa HDACs (HDAC4, 5, and 7) are phosphorylated and excluded from the nucleus by AMPK family kinases. In response to the fasting hormone glucagon, class IIa HDACs are rapidly dephosphorylated and translocated to the nucleus where they associate with the promoters of gluconeogenic enzymes such as G6Pase. In turn, HDAC4/5 recruit HDAC3, which results in the acute transcriptional induction of these genes via deacetylation and activation of FOXO family transcription factors. Loss of class IIa HDACs in murine liver results in inhibition of FOXO target genes and lowers blood glucose, resulting in increased glycogen storage. Finally, suppression of class IIa HDACs in mouse models of type 2 diabetes ameliorates hyperglycemia, suggesting that inhibitors of class I/II HDACs may be potential therapeutics for metabolic syndrome.

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    • "Exercise induced a similar increase in NAD + content and a decrease in acetylation of p53, implying a similar activation of the NAD + dependent deacetylase SIRT1 in both genotypes. Likewise, exercise decreased HDAC4 phosphorylation similarly in the two genotypes, which is expected to result in a similar exclusion of HDAC4 from the nucleus, thereby activating FoxO1 (Mihaylova et al., 2011) and accordingly inducing PDK4 transcription. Collectively, this supports the finding of a similar exercise-induced increase in PDK4 mRNA in the two genotypes. "
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    • "Since FOXO1 target genes can be stimulated by forskolin through mimicking the glucagon signaling pathway30,41, we further analyzed the FOXO1 target gene expression in LMKO and control primary hepatocytes. We found that the expression of Irs2, Igfbp1, Pck1 and G6pc was lower in LMKO primary hepatocytes than that in control cells upon forskolin treatment, confirming that MED23 plays a key role in controlling gluconeogenic gene expression (Figure 2I-2L). "
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    ABSTRACT: Mediator complex is a molecular hub integrating signaling, transcription factors, and RNA polymerase II (RNAPII) machinery. Mediator MED23 is involved in adipogenesis and smooth muscle cell differentiation, suggesting its role in energy homeostasis. Here, through the generation and analysis of a liver-specific Med23-knockout mouse, we found that liver Med23 deletion improved glucose and lipid metabolism, as well as insulin responsiveness, and prevented diet-induced obesity. Remarkably, acute hepatic Med23 knockdown in db/db mice significantly improved the lipid profile and glucose tolerance. Mechanistically, MED23 participates in gluconeogenesis and cholesterol synthesis through modulating the transcriptional activity of FOXO1, a key metabolic transcription factor. Indeed, hepatic Med23 deletion impaired the Mediator and RNAPII recruitment and attenuated the expression of FOXO1 target genes. Moreover, this functional interaction between FOXO1 and MED23 is evolutionarily conserved, as the in vivo activities of dFOXO in larval fat body and in adult wing can be partially blocked by Med23 knockdown in Drosophila. Collectively, our data revealed Mediator MED23 as a novel regulator for energy homeostasis, suggesting potential therapeutic strategies against metabolic diseases.Cell Research advance online publication 16 September 2014; doi:10.1038/cr.2014.120.
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    • "Administration of oleanolic acid stimulates AMPK activity which leads to an increased inhibitory phosphorylation of class IIa HDACs. The suppression of class IIa HDACs (and their possible reduction in the nucleus) induces acetylation and phosphorylation of FoxO1 as suggested [14]. The sustained inactivation of FoxO1 either by its acetylation and/or phosphorylation may contribute to the persistent anti-hyperglycemia effect of OA on HF-STZ induced T2D mice. "
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    ABSTRACT: Our recent study (referred as Study 1) showed that the triterpenoid oleanolic acid (OA) was able to produce a sustained correction of hyperglycemia beyond treatment period in type 2 diabetes (T2D) mice with liver as a responsible site. To follow up the previous observations, the present study (referred as Study 2) investigated the possible role of acetylation of FoxO1 and associated events in this therapeutic memory by characterizing the pathways regulating the acetylation status during and post-OA treatments. OA treatment (100 mg/kg/day for 4 weeks, during OA treatment) reduced hyperglycemia in T2D mice by ∼87% and this effect was largely (∼70%) maintained even 4 weeks after the cessation of OA administration (post-OA treatment). During OA treatment, the acetylation and phosphorylation of FoxO1 were markedly increased (1.5 to 2.5-fold) while G6Pase expression was suppressed by ∼80%. Consistent with this, OA treatment reversed pyruvate intolerance in high-fat fed mice. Histone acetyltransferase 1 (HAT1) content was increased (>50%) and histone deacetylases (HDACs) 4 and 5 (not HDAC1) were reduced by 30-50%. The OA-induced changes in FoxO1, G6Pase, HAT1 and HDACs persisted during the post-OA treatment period when the increased phosphorylation of AMPK, SIRT1 content and reduced liver triglyceride had subsided. These results confirmed the ability of OA to control hyperglycemia far beyond treatment period in T2D mice. Most importantly, in the present study we demonstrated acetylation of FoxO1 in the liver is involved in OA-induced memory for the control of hyperglycemia. Our novel findings suggest that acetylation of the key regulatory proteins of hepatic gluconeogenesis is a plausible mechanism by the triterpenoid to achieve a sustained glycemic control for T2D.
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