Insulin regulation of GnRH gene expression through MAP kinase signaling pathways.
In mammals, reproduction is acutely regulated by metabolic status. Insulin is an important nutritional signal from the periphery that may regulate the reproductive axis. To determine whether insulin acts directly on the GnRH neuron, we performed studies in mouse-derived GnRH-expressing cell lines. Both insulin receptor protein and mRNA were detected in these cells. A saturation radioligand binding assay revealed high affinity, low capacity binding sites for insulin in GnRH neurons. Insulin also stimulated GnRH promoter activity in GnRH neurons. This effect was blocked by pretreatment with the MEK inhibitor, PD98059, indicating a role for MAP kinase signaling. In transient transfection studies, insulin treatment stimulated expression of a 1250 bp mouse GnRH gene promoter fragment four-fold when compared to promoter activity in untreated cells. In contrast, insulin did not stimulate activity of a 587 bp fragment of the mGnRH gene promoter, indicating that the promoter elements mediating insulin stimulation of the GnRH promoter are located between -1250 and -587 bp. Our studies suggest that insulin may regulate reproductive function by direct effects on the GnRH neurons and specifically by stimulating GnRH gene expression.
Kim
Helen H
HH
University of Chicago, Department of Obstetrics and Gynecology, 5839 South Maryland Avenue MC5053, Chicago, IL 60637, USA.
DiVall
Sara A
SA
Deneau
Robyn M
RM
Wolfe
Andrew
A
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter / Q000235:genetics; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics* / Q000378:metabolism; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D005419:Flavonoids; D007328:Insulin; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D011972:Receptor, Insulin; D048049:Extracellular Signal-Regulated MAP Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one