The Effect of AMP‐Activated Kinase Activation on Gonadotrophin‐Releasing Hormone Secretion in GT1‐7 Cells and its Potential Role in Hypothalamic Regulation of the Oestrous Cyclicity in Rats

Jan 16, 2008Journal of neuroendocrinology

How activating cell energy sensors affects hormone release controlling the reproductive cycle in rat brain cells

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Abstract

Phosphorylation of AMPK in hypothalamic neurons was significantly increased following treatment with 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside (AICAR) or metformin.

Each subunit of AMPK is present in immortalized GnRH neurons.
AICAR and metformin treatment increased phosphorylation of AMPKalpha at Thr172 and acetyl-CoA carboxylase at ser79.
AICAR and metformin inhibited GnRH release in a dose-dependent manner.
In vivo administration of AICAR increased food intake in female rats 24 hours after injection.
The interval between two oestrous stages was significantly shorter in the AICAR group compared to the saline group over four weeks.

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Hypothalamic AMP-activated kinase (AMPK) is a key regulator of food intake in mammals. Its role in reproduction at the central level and, more precisely, in gonadotrophin-releasing hormone (GnRH) release has never been investigated. We showed that each subunit of AMPK is present in immortalised GnRH neurones (GT1-7 cells). Treatment with 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside (AICAR) and metformin, two activators of AMPK, increased dose-dependent and time-dependent phosphorylation of AMPKalpha atThr172 in GT1-7 cells. Phosphorylation of acetyl-coenzyme A carboxylase at ser79 also increased. Treatment with AICAR (5 mM) or metformin (5 mM) for 4 h inhibited GnRH release in the presence or absence of GnRH (10(-8) M). Specific AMPK inhibitor compound C completely eliminated the effects of AICAR or metformin on GnRH release. Finally, we determined the central effects of AICAR in vivo on food intake and oestrous cyclicity. Ten-week-old female rats received a 50 microg AICAR or a saline i.c.v. injection. We detected increased AMPK and acetyl-CoA carboxylase phosphorylation, specifically in the hypothalamus, 30 min after AICAR injection. Food intake was significantly higher (P < 0.05) in animals treated with AICAR than in animals injected with saline, 24 h after injection. This effect was abolished after 1 week. Moreover, during the 4 weeks following injection, the interval between two oestrous stages was significantly lower in the AICAR group than in the saline group. Our findings suggest that AMPK activation may act directly at the hypothalamic level to affect fertility by modulating GnRH release and oestrous cyclicity.

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The Effect of AMP‐Activated Kinase Activation on Gonadotrophin‐Releasing Hormone Secretion in GT1‐7 Cells and its Potential Role in Hypothalamic Regulation of the Oestrous Cyclicity in Rats

Abstract

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