Metformin suppresses pregnane X receptor (PXR)-regulated transactivation of CYP3A4 gene

Lucie Krausova, Lucie Stejskalova, Hongwei Wang, Radim Vrzal, Zdenek Dvorak, Sridhar Mani, Petr Pavek

Research output: Contribution to journalArticle

50 Scopus citations

Abstract

Metformin is widely used in the treatment of type-2 diabetes. The pleotropic effects of metformin on glucose and lipid metabolism have been proposed to be mediated by the activation of AMP-activated protein kinase (AMPK) and the subsequent up-regulation of small heterodimer partner (SHP). SHP suppresses the functions of several nuclear receptors involved in the regulation of hepatic metabolism, including pregnane X receptor (PXR), which is referred to as a "master regulator" of drug/xenobiotic metabolism. In this study, we hypothesize that metformin suppresses the expression of CYP3A4, a main detoxification enzyme and a target gene of PXR, due to SHP up-regulation. We employed various gene reporter assays in cell lines and qRT-PCR in human hepatocytes and in Pxr -/- mice. We show that metformin dramatically suppresses PXR-mediated expression of CYP3A4 in hepatocytes. Consistently, metformin significantly suppressed the up-regulation of Cyp3a11 mRNA in the liver and intestine of wild-type mice, but not in Pxr -/- mice. A mechanistic investigation of the phenomenon showed that metformin does not significantly up-regulate SHP in human hepatocytes. We further demonstrate that AMPK activation is not involved in this process. We show that metformin disrupts PXR's interaction with steroid receptor coactivator-1 (SRC1) in a two-hybrid assay independently of the PXR ligand binding pocket. Metformin also inhibited vitamin D receptor-, glucocorticoid receptor- and constitutive androstane receptor (CAR)-mediated induction of CYP3A4 mRNA in human hepatocytes. We show, therefore, a suppressive effect of metformin on PXR and other ligand-activated nuclear receptors in transactivation of the main detoxification enzyme CYP3A4 in human hepatocytes.

Original languageEnglish (US)
Pages (from-to)1771-1780
Number of pages10
JournalBiochemical Pharmacology
Volume82
Issue number11
DOIs
StatePublished - Dec 1 2011

Keywords

  • AMPK
  • Cytochrome P450
  • Induction
  • Metformin
  • PXR

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology

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