Thiazolidinediones Inhibit Aromatase Activity in Human Granulosa Cells by Interfering with Androgen Binding to Aromatase Takako Araki M.D. Dimiter Avtanski.

Thiazolidinediones Inhibit Aromatase Activity in Human Granulosa Cells by Interfering with Androgen Binding to

Aromatase

Takako Araki M.D. Dimiter Avtanski PhD Grishma Parikh M.D. Michael Goldman M.D. Zev Rosenwaks M.D.

Leonid Poretsky M.D. Donna Seto-Young PhD.

Department of MedicineDivision of Endocrinology & Metabolism

Beth Israel Medical CenterAlbert Einstein College of Medicine

New York, NY

• Insulin plays a role in human ovarian function

• Among other effects, insulin regulates steroidogenesis,

upregulates insulin-like growth factor 1 receptors,

and inhibits insulin-like growth factor binding protein 1

production in human ovary

Role of Insulin in Human Ovary

Hyperinsulinemia stimulates ovarian growth and cyst formation, probably contributing to the pathogenesis of polycystic ovary syndrome (PCOS)

Treatment of PCOS Weight loss: lifestyle modifications via diet

and exercise

Regulation of menstrual cycles: oral contraceptives

Anti-androgens: spironolactone

Insulin-sensitizing agents: metformin, thiazolidinediones (TZDs)

• TZDs are a group of medications used as insulin sensitizers in treatment of diabetes • TZDs, acting as PPAR- agonists, enhance insulin sensitivity of tissues and improve glucose tolerance in patients with insulin resistant states

• TZDs reduce hyperandrogenemia and restore ovulation in PCOS

Thiazolidinediones (TZDs)

AromataseAromataseCytochrome P-450 superfamilyCytochrome P-450 superfamilyProduct of the CYP19 geneProduct of the CYP19 geneHeme structure is responsible for binding Heme structure is responsible for binding androgenic steroidandrogenic steroidHighly expressed in placenta and granulosa Highly expressed in placenta and granulosa cellscellsKey enzyme that regulates estrogen Key enzyme that regulates estrogen synthesis in ovarysynthesis in ovaryPresent in subcutaneous fat (adipose Present in subcutaneous fat (adipose tissue), fetal liver, muscle, brain, bone, tissue), fetal liver, muscle, brain, bone, breast, and testisbreast, and testis

Cholesterol

Estradiol

Estrone

Pregnenolone 17-hydroxypregnelone DHEA

17-hydroxyprogesterone

Aromatase

Aromatase

3 Beta HSD 3 Beta HSD 3 Beta HSD

17 Alpha

17 Alpha

17-20 lyase

17-20 lyase

17 Beta HSD

17 Beta HSD

StAR/SCC

Progesterone

Testosterone

Androstenedione

17-hydroxysteroid dehydrogenase:17-HSD

Aromatase InhibitorAromatase InhibitorType 1 Inhibitors: Steroidal Inhibitors

Type 2 Inhibitors: Non-steroidal Inhibitors

Androstenedione Estrone

TZDs inhibit estrone productionTZDs effect was abolished when aromatase activity was inhibited

Testosterone Estradiol

TZDs inhibit estradiol productionTZDs effect was abolished when aromatase activity was inhibited

Aromatase mRNA ExpressionAromatase mRNA Expression

Aromatase mRNA expression was not changed by TZDs

Aromatase Enzyme ExpressionAromatase Enzyme Expression

Aromatase enzyme expression was not changed by TZDs

TZD Effect on Substrate bindingto Aromatase

TZDs inhibit aromatase activity by interfering with substrate binding

1/V

1/S0

Competitive Inhibitor

Competitive Inhibitor

No Inhibitor

1/Km

Vmax

1/S

1/V

0

Non-competitive Inhibitor

Non-competitive Inhibitor

No Inhibitor

1/Km

Vmax

1/V

1/S0

Uncompetitive Inhibitor

Uncompetitive Inhibitor

No Inhibitor

1/Km

Vmax

Kinetic Study - Estradiol -

Km 6.4Km 11.3Km 7.3Km 10.6Km 9.8

SummarySummary~~in Human Granulosa Cells~in Human Granulosa Cells~

TZDs inhibit estrogen productionTZDs inhibit estrogen production

TZDs do not change aromatase mRNA or TZDs do not change aromatase mRNA or enzyme protein expressionenzyme protein expression

TZDs inhibit aromatase activity by interfering TZDs inhibit aromatase activity by interfering with androgen binding to aromatase, acting with androgen binding to aromatase, acting as uncompetitive inhibitorsas uncompetitive inhibitors

TZDs as Aromatase Inhibitors TZDs as Aromatase Inhibitors ~ ~ Future Directions and Future Directions and

Possible Clinical Implications Possible Clinical Implications ~~

Potential use in estrogen – dependent Potential use in estrogen – dependent diseases:diseases:Breast cancerBreast cancerEndometriosisEndometriosis

Our findings may explain in partOur findings may explain in part

the relationship between TZDs and the relationship between TZDs and osteoporosisosteoporosis

Thank youWe are thankful for the support fromWe are thankful for the support from

Gerald J. and Dorothy R. Friedman Gerald J. and Dorothy R. Friedman FoundationFoundation