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Diabetologia. 2014 Dec;57(12):2576-85. doi: 10.1007/s00125-014-3366-x. Epub 2014 Sep 10.

PKB/Akt phosphorylation of ERRγ contributes to insulin-mediated inhibition of hepatic gluconeogenesis.

Author information

1
National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, 500-757, Republic of Korea.

Abstract

AIMS/HYPOTHESIS:

Insulin resistance, a major contributor to the pathogenesis of type 2 diabetes, leads to increased hepatic glucose production (HGP) owing to an impaired ability of insulin to suppress hepatic gluconeogenesis. Nuclear receptor oestrogen-related receptor γ (ERRγ) is a major transcriptional regulator of hepatic gluconeogenesis. In this study, we investigated insulin-dependent post-translational modifications (PTMs) altering the transcriptional activity of ERRγ for the regulation of hepatic gluconeogenesis.

METHODS:

We examined insulin-dependent phosphorylation and subcellular localisation of ERRγ in cultured cells and in the liver of C57/BL6, leptin receptor-deficient (db/db), liver-specific insulin receptor knockout (LIRKO) and protein kinase B (PKB) β-deficient (Pkbβ (-/-)) mice. To demonstrate the role of ERRγ in the inhibitory action of insulin on hepatic gluconeogenesis, we carried out an insulin tolerance test in C57/BL6 mice expressing wild-type or phosphorylation-deficient mutant ERRγ.

RESULTS:

We demonstrated that insulin suppressed the transcriptional activity of ERRγ by promoting PKB/Akt-mediated phosphorylation of ERRγ at S179 and by eliciting translocation of ERRγ from the nucleus to the cytoplasm through interaction with 14-3-3, impairing its ability to promote hepatic gluconeogenesis. In addition, db/db, LIRKO and Pkbβ (-/-) mice displayed enhanced ERRγ transcriptional activity due to a block in PKBβ-mediated ERRγ phosphorylation during refeeding. Finally, the phosphorylation-deficient mutant ERRγ S179A was resistant to the inhibitory action of insulin on HGP.

CONCLUSIONS/INTERPRETATION:

These results suggest that ERRγ is a major contributor to insulin action in maintaining hepatic glucose homeostasis.

PMID:
25205222
DOI:
10.1007/s00125-014-3366-x
[Indexed for MEDLINE]

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