Hypothalamic preproghrelin gene expression is repressed by insulin via both PI3-K/Akt and ERK1/2 MAPK pathways in immortalized, hypothalamic neurons.
The gut peptide ghrelin is expressed within neurons of the hypothalamus. Using a hypothalamic cell line, mHypoE-38 neurons, the effect of insulin on preproghrelin gene expression was assayed. These cells contain neuron-specific markers, preproghrelin and the insulin receptor. We determined that insulin has direct effects on preproghrelin gene expression. Insulin (10 nM) stimulated protein kinase B (Akt) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation from 5 to 60 min and 5 min, respectively, and led to repression of preproghrelin gene expression at 2 h. Pharmacological inhibitors to phosphoinositide-3-kinase (PI3-K; LY294002) and MEK (PD98059) demonstrated that basal ghrelin gene expression is regulated by the PI3-K pathway and requires the mitogen-activated protein kinase pathway for insulin-stimulated preproghrelin repression. These results demonstrate that insulin has a direct effect on hypothalamic neurons to decrease preproghrelin gene expression through classic insulin pathways.
Fick
L J
LJ
Department of Physiology, University of Toronto, Ont., Canada.
Cai
F
F
Belsham
D D
DD
D000818:Animals; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D015536:Down-Regulation; D005419:Flavonoids / Q000494:pharmacology; D054439:Ghrelin / Q000235:genetics*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011972:Receptor, Insulin / Q000819:agonists* / Q000378:metabolism
D002867:Chromones; D005419:Flavonoids; D054439:Ghrelin; D007328:Insulin; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one