Mechanisms by Which Membrane and Nuclear ER Alpha Inhibit Adipogenesis in Cells Isolated From Female Mice

Area of Science:

• Endocrinology
• Molecular Biology
• Cell Biology

Background:

• Dysfunctional visceral adipocytes increase post-menopause, contributing to metabolic alterations.
• Estrogen receptors alpha (ERα), both membrane-bound and nuclear, are known to suppress adipogenesis.
• The precise mechanisms by which ERα pools regulate adipogenesis remain incompletely understood.

Purpose of the Study:

• To elucidate the collaborative mechanisms of membrane and nuclear ERα in inhibiting adipogenesis.
• To identify the molecular players involved in ERα-mediated suppression of the PPARγ gene.
• To understand how estrogen signaling impacts progenitor cell differentiation into adipocytes.

Main Methods:

• Utilized 3T3-L1 pre-adipocytes and adipose-derived stem cells (ADSC).
• Investigated signaling pathways involving phosphatidylinositol 3-kinase (PI3K) and protein kinase B (AKT).
• Assessed gene expression of PPARγ, Wnt1, and Wnt10b.
• Analyzed the recruitment of co-repressors GATA3, β-catenin, and TCF4 to the PPARγ promoter.
• Examined the effect of estrogen on rosiglitazone-induced adipocyte differentiation.

Main Results:

• Membrane ERα signaling activates PI3K-AKT pathway, enhancing nuclear ERα localization at the PPARγ promoter.
• AKT signaling increases co-repressor abundance (GATA3, β-catenin, TCF4) at the PPARγ promoter.
• Membrane ERα signaling upregulates Wnt1 and Wnt10b expression.
• Estrogen-mediated inhibition of adipocyte differentiation requires the identified repressor complex components.

Conclusions:

• ERα cellular pools cooperate to inhibit PPARγ gene expression, thereby limiting adipocyte differentiation.
• The PI3K-AKT-mediated pathway is central to ERα's regulation of adipogenesis.
• Understanding these mechanisms offers insights into metabolic regulation in postmenopausal women.