Ovarian signalling pathways regulated by leptin during the ovulatory process

Area of Science:

• Reproductive endocrinology
• Molecular signaling pathways
• Ovarian function

Background:

• Leptin, a hormone produced by adipose tissue, influences reproductive processes.
• Leptin exhibits dual effects, both stimulating and inhibiting ovulation.
• The underlying molecular mechanisms of leptin's opposing actions on ovulation require elucidation.

Purpose of the Study:

• To investigate how different leptin concentrations modulate ovarian signaling pathways.
• To determine the role of STAT3 and ERK1/2 phosphorylation and SOCS3 expression in leptin's effects on ovulation.
• To explore the involvement of JAK/STAT and MAPK pathways in leptin-mediated steroidogenesis.

Main Methods:

• In vivo and in vitro experiments using gonadotropin-primed immature rats.
• Acute and daily leptin administration to assess ovulation.
• Ovarian explant cultures to study direct cellular responses to leptin.
• Analysis of STAT3 and ERK1/2 phosphorylation and SOCS3 protein/mRNA expression.
• Inhibition of JAK/STAT and MAPK pathways to assess their role in leptin's effects.

Main Results:

• Acute leptin inhibited ovulation, decreasing STAT3/ERK1/2 phosphorylation and increasing SOCS3.
• Low-dose daily leptin stimulated ovulation, increasing STAT3/ERK1/2 phosphorylation and decreasing SOCS3.
• Leptin modulated STAT3 and ERK1/2 activation and SOCS3 expression in ovarian explants.
• Inhibitors of JAK/STAT and MAPK pathways blocked leptin's effects on progesterone secretion.

Conclusions:

• Leptin concentration-dependently regulates ovarian STAT3, ERK1/2, and SOCS3.
• Leptin's dual action on ovulation and steroidogenesis involves the ERK and STAT signaling cascades.
• These findings provide insights into the intricate regulation of the ovulatory process by leptin.