Hepatic insulin resistance following chronic activation of the CREB coactivator CRTC2

Meghan F. Hogan, Kim Ravnskjaer, Shigenobu Matsumura, Mark O. Huising, Rebecca L. Hull, Steven E. Kahn, Marc Montminy

Research output: Contribution to journalArticlepeer-review

Abstract

Under fasting conditions, increases in circulating concentrations of glucagon maintain glucose homeostasis via the induction of hepatic gluconeogenesis. Triggering of the cAMP pathway in hepatocytes stimulates the gluconeogenic program via the PKA-mediated phosphorylation of CREB and dephosphorylation of the cAMP-regulated CREB coactivators CRTC2 and CRTC3. In parallel, decreases in circulating insulin also increase gluconeogenic gene expression via the de-phosphorylation and activation of the forkhead transcription factor FOXO1. Hepatic gluconeogenesis is increased in insulin resistance where it contributes to the attendant hyperglycemia. Whether selective activation of the hepatic CREB/CRTC pathway is sufficient to trigger metabolic changes in other tissues is unclear, however. Modest hepatic expression of a phosphorylation-defective and therefore constitutively active CRTC2S171,275A protein increased gluconeogenic gene expression under fasting as well as feeding conditions. Circulating glucose concentrations were constitutively elevated in CRTC2S171,275A-expressing mice, leading to compensatory increases in circulating insulin concentrations that enhance FOXO1 phosphorylation. Despite accompanying decreases in FOXO1 activity, hepatic gluconeogenic gene expression remained elevated in CRTC2S171,275A mice, demonstrating that chronic increases inCRTC2activity in the liver are indeed sufficient to promote hepatic insulin resistance and to disrupt glucose homeostasis.

Original languageEnglish (US)
Pages (from-to)25997-26006
Number of pages10
JournalJournal of Biological Chemistry
Volume290
Issue number43
DOIs
StatePublished - Oct 23 2015

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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