Metformin inhibits StAR expression in human endometriotic stromal cells via AMPK-mediated disruption of CREB-CRTC2 complex formation.

Abstract

CONTEXT:

Endometriosis is an estrogen-dependent disease affecting reproductive women. Metformin could have a therapeutic effect on endometriosis through regulation of local estrogen production.

OBJECTS:

The aim of this study was to investigate the molecular and cellular mechanism by which metformin regulates StAR expression in human endometriotic stromal cells (ESCs).

METHODS:

ESCs derived from ovarian endometriomas were cultured with metformin and prostaglandin E2 (PGE2). StAR mRNA was measured by quantitative PCR; pregnenolone, progesterone, and estrogen production were measured by ELISA kits; steroidogenic acute regulatory protein (StAR), AMP-activated protein kinase, cAMP response element binding protein (CREB), and CREB-regulated transcription coactivator 2 (CRTC2) protein expression were measured by Western blot assay; and CRTC2 translocation and its association with CREB were assessed by coimmunoprecipitation assay and CRTC2-CREB complex binding by a chromatin immunoprecipitation assay.

RESULTS:

1) StAR mRNA levels in ESCs are 264 times higher than those in endometrial cells. 2) Metformin downregulates the StAR mRNA expression (maximum 31.7%) stimulated by PGE2 (2.4-fold) in ESCs. 3) PGE2 induces CRTC2 translocation and enhances its association with CREB to form a transcription complex that binds to the StAR promoter region. 4) Metformin prevents the nuclear translocation of CRTC2 by increasing AMP-activated protein kinase phosphorylation. This inhibits transcription of StAR by disrupting formation of the CREB-CRTC2 complex, involved in activation of the StAR promoter cAMP response element.

CONCLUSIONS:

We have demonstrated a detailed mechanistic analysis of StAR expression regulated by metformin in ESCs. Our data highlight a role for CRTC2 in the mechanism by which metformin inhibits StAR expression.

• Authors: Jia-Ning Xu, Cheng Zeng, Yan Zhou, Chao Peng, Ying-Fang Zhou, Qing Xue
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 99 Issue 8 Pg. 2795-803 (Aug 2014) ISSN: 1945-7197 [Electronic] United States
• PMID: 24823468 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• CREB1 protein, human
• CRTC2 protein, human
• Cyclic AMP Response Element-Binding Protein
• Phosphoproteins
• Transcription Factors
• steroidogenic acute regulatory protein
• Metformin
• AMP-Activated Protein Kinases

Topics

• AMP-Activated Protein Kinases (metabolism)
• Adult
• Cells, Cultured
• Cyclic AMP Response Element-Binding Protein (metabolism)
• Down-Regulation (drug effects, genetics)
• Endometrium (drug effects, metabolism)
• Female
• Humans
• Metformin (pharmacology)
• Phosphoproteins (genetics, metabolism)
• Phosphorylation (drug effects)
• Protein Binding (drug effects)
• Signal Transduction (drug effects, genetics)
• Stromal Cells (drug effects, metabolism)
• Transcription Factors (metabolism)