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Intracerebroventricular Administration of Metformin Inhibits Ghrelin-Induced Hypothalamic AMP-Kinase Signalling and Food Intake.
MedLine Citation:
PMID:  22343549     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Background/Aims: The antihyperglycaemic drug metformin reduces food consumption through mechanisms that are not fully elucidated. The present study investigated the effects of intracerebroventricular administration of metformin on food intake and hypothalamic appetite-regulating signalling pathways induced by the orexigenic peptide ghrelin. Methods: Rats were injected intracerebroventricularly with ghrelin (5 μg), metformin (50, 100 or 200 μg), 5-amino-imidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR, 25 μg) and L-leucine (1 μg) in different combinations. Food intake was monitored during the next 4 h. Hypothalamic activation of AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), regulatory-associated protein of mTOR (Raptor), mammalian target of rapamycin (mTOR) and p70 S6 kinase 1 (S6K) after 1 h of treatment was analysed by immunoblotting. Results: Metformin suppressed the increase in food consumption induced by intracerebroventricular ghrelin in a dose-dependent manner. Ghrelin increased phosphorylation of hypothalamic AMPK and its targets ACC and Raptor, which was associated with the reduced phosphorylation of mTOR. The mTOR substrate, S6K, was activated by intracerebroventricular ghrelin despite the inhibition of mTOR. Metformin treatment blocked ghrelin-induced -activation of hypothalamic AMPK/ACC/Raptor and restored mTOR activity without affecting S6K phosphorylation. Metformin also reduced food consumption induced by the AMPK activator AICAR while the ghrelin-triggered food intake was inhibited by the mTOR activator L-leucine. Conclusion: Metformin could reduce food intake by preventing ghrelin-induced AMPK signalling and mTOR inhibition in the hypotalamus.
Authors:
Darko Stevanovic; Kristina Janjetovic; Maja Misirkic; Ljubica Vucicevic; Mirjana Sumarac-Dumanovic; Dragan Micic; Vesna Starcevic; Vladimir Trajkovic
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-2-14
Journal Detail:
Title:  Neuroendocrinology     Volume:  -     ISSN:  1423-0194     ISO Abbreviation:  -     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-2-20     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0035665     Medline TA:  Neuroendocrinology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 S. Karger AG, Basel.
Affiliation:
Institutes of Medical Physiology, University of Belgrade, Belgrade, Serbia.
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