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Metformin: direct inhibition of rat ovarian theca-interstitial cell proliferation
Matthew A Will1, Murugesan Palaniappan, Helle Peegel
1Department of Obstetrics and Gynecology, University of Michigan Medical School, Ann Arbor, Michigan, USA. matwill@med.umich.edu
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).
Insights
Metformin directly reduces ovarian theca-interstitial cell proliferation by activating adenosine monophosphate-activated protein kinase (AMPK). This suggests metformin
Area of Science:
- Endocrinology and reproductive biology.
- Cellular and molecular mechanisms of cell growth regulation.
Background:
- Ovarian theca-interstitial (T-I) cells play a crucial role in ovarian function.
- Hyperinsulinemia can lead to excessive T-I cell proliferation, contributing to conditions like polycystic ovary syndrome (PCOS).
- Metformin is a widely used drug for type 2 diabetes with potential applications in PCOS.
Purpose of the Study:
- To investigate the direct impact of metformin on ovarian T-I cell proliferation.
- To elucidate the role of adenosine monophosphate-activated protein kinase (AMPK) in mediating metformin's effects on these cells.
Main Methods:
- In vitro study using cultured ovarian T-I cells isolated from immature Sprague-Dawley rats.
- Cells were treated with insulin, metformin, and specific activators/inhibitors of AMPK (AICAR, compound C).
- Proliferation was assessed by measuring cell cycle proteins (cyclin D3, CDK4) and DNA synthesis (BrdU incorporation). AMPK activation was confirmed via Western blot analysis.
Main Results:
- Metformin significantly inhibited insulin-induced proliferation of ovarian T-I cells.
- Metformin dose-dependently activated AMPK.
- The drug suppressed insulin-induced activation of Erk1/2 and S6K1, an effect reversed by an AMPK inhibitor.
Conclusions:
- Metformin exerts a direct inhibitory effect on ovarian T-I cell proliferation through an AMPK-dependent pathway.
- These findings support the therapeutic potential of metformin in managing conditions characterized by hyperinsulinemia and excessive T-I cell growth, such as PCOS.
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