Metformin: Direct Inhibition of Rat Ovarian Theca-Interstitial Cell Proliferation

Capsule:
Metformin activates adenosine monophosphate–activated protein kinase (AMPK) in rat ovarian thecainterstitial cells and subsequently inhibits cell proliferation and insulin-induced mitogenic signaling pathways.

Authors:
Matthew A. Will, M.D., Murugesan Palaniappan, Ph.D., Helle Peegel, M.S., Pradeep Kayampilly, Ph.D., K.M.J. Menon, Ph.D.
Volume 98, Issue 1, Pages 207-214, July 2012

Objective:
To determine whether metformin has direct effects on ovarian theca-interstitial (T-I) cell proliferation through activation of adenosine monophosphate–activated protein kinase (AMPK).

Design:
In vitro experimental study.

Setting:
Academic medical center laboratory.

Animal(s):
Immature Sprague-Dawley female rats.

Intervention(s):
Ovarian T-I cells were isolated, purified, and cultured in the absence (control) or presence of insulin (1 μg/mL) with or without metformin or other activators/inhibitors of AMPK (AICAR, compound C).

Main Outcome Measure(s):
Proliferation assessed by determination of expression levels of proteins involved in cell cycle progression, cyclin D3, and cyclin-dependent kinase 4 (CDK4) with Western blot analysis, and determination of DNA synthesis with bromodeoxyuridine (BrdU) incorporation assay; activation of AMPK, Erk1/2, and S6K1 determined by Western blot analysis with the use of antibodies specific for the phosphorylated (activated) forms.

Result(s):
Metformin inhibited insulin-induced ovarian T-I cell proliferation and the up-regulation of the cell cycle regulatory proteins, cyclin D3 and CDK4. Metformin independently activated AMPK in a dose-dependent manner. Treatment with metformin inhibited insulin-induced activation of Erk1/2 and S6K1. This effect was reversed with the addition of compound C, a known AMPK inhibitor.

Conclusion(s):
Metformin directly inhibits proliferation of ovarian T-I cells via an AMPK-dependent mechanism. These findings further validate the potential benefits of metformin in the treatment of conditions associated with hyperinsulinemia and excessive growth of ovarian T-I cells (such as polycystic ovary syndrome).

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