Activated AMPK inhibits PPAR-α and PPAR-γ transcriptional activity in hepatoma cells

Margaret S. Sozio, Changyue Lu, Yan Zeng, Suthat Liangpunsakul, David W. Crabb

Research output: Contribution to journalArticlepeer-review

71 Scopus citations

Abstract

AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor- α(PPAR-α) are critical regulators of short-term and long-term fatty acid oxidation, respectively. We examined whether the activities of these molecules were coordinately regulated. H4IIEC3 cells were transfected with PPAR-α and PPAR-γ expression plasmids and a peroxisome-proliferator-response element (PPRE) luciferase reporter plasmid. The cells were treated with PPAR agonists (WY-14,643 and rosiglitazone), AMPK activators 5-aminoimidazole-4-carboxamide riboside (AICAR) and metformin, and the AMPK inhibitor compound C. Both AICAR and metformin decreased basal and WY-14,643- stimulated PPAR-α activity; compound C increased agonist-stimulated reporter activity and partially reversed the effect of the AMPK activators. Similar effects on PPAR-γ were seen, with both AICAR and metformin inhibiting PPRE reporter activity. Compound C increased basal PPAR-γ activity and rosiglitazone-stimulated activity. In contrast, retinoic acid receptor-α (RAR-α), another nuclear receptor that dimerizes with retinoid X receptor (RXR), was largely unaffected by the AMPK activators. Compound C modestly increased AM580 (an RAR agonist)-stimulated activity. The AMPK activators did not affect PPAR-α binding to DNA, and there was no consistent correlation between effects of the AMPK activators and inhibitor on PPAR and the nuclear localization of AMPK-α subunits. Expression of either a constitutively active or dominant negative AMPK-α inhibited basal and WY-14,643-stimulated PPAR-α activity and basal and rosiglitazone-stimulated PPAR-γ activity. We concluded that the AMPK activators AICAR and metformin inhibited transcriptional activities of PPAR-α and PPAR-γ, whereas inhibition of AMPK with compound C activated both PPARs. The effects of AMPK do not appear to be mediated through effects on RXR or on PPAR/RXR binding to DNA. These effects are independent of kinase activity and instead appear to rely on the activated conformation of AMPK. AMPK inhibition of PPAR-α and -γ may allow for short-term processes to increase energy generation before the cells devote resources to increasing their capacity for fatty acid oxidation.

Original languageEnglish (US)
Pages (from-to)G739-G747
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume301
Issue number4
DOIs
StatePublished - Oct 2011

Keywords

  • AMP-activated protein kinase
  • Compound C
  • Fatty acid oxidation
  • Nuclear receptors
  • Peroxisome proliferator-activated receptor

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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