Molecular mechanisms for activation of the agouti-related protein and stimulation of appetite.
OBJECTIVE
The agouti-related protein (Agrp) is a powerful orexigenic peptide, but little is known about its transcriptional regulation. The objective of this study was to determine molecular mechanisms for the activation of hypothalamic Agrp and identify compounds that stimulate appetite.


METHODS
We used promoter analyses methods, hypothalamic cell culture and transfection, immunohistochemistry, luciferase-expressing transgenic mice, in vivo bioluminescence, anitisense RNA, mouse feeding studies, indirect calorimetry, real-time PCR, and Western blots.


RESULTS
We found that the Krüppel-like factor 4 (Klf4) is a potent activator of Agrp by binding to a specific CACCC-box in its minimal promoter. We also found that an extract of tarragon, termed PMI-5011, activated hypothalamic Klf4 and Agrp. In vivo, PMI-5011 increased Agrp promoter activity in luciferase-expressing transgenic mice, increased hypothalamic Klf4 and Agrp expression, increased hypothalamic Orexin and melanin-concentrating hormone, increased food intake, reduced circulating insulin and leptin levels, attenuated energy expenditure, and enhanced body weight but only when using a high-fat diet.


CONCLUSIONS
These data show that Klf4 augmented hypothalamic Agrp by binding to a specific CACCC-box onto its minimal promoter. In addition, the tarragon extract PMI-5011 activated Klf4 and orexigenic neuropeptides and reduced peripheral insulin and leptin levels leading to positive energy balance.
Ilnytska
Olha
O
Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, USA.
Stütz
Adrian M
AM
Park-York
MieJung
M
York
David A
DA
Ribnicky
David M
DM
Zuberi
Aamir
A
Cefalu
William T
WT
Argyropoulos
George
G
D054369:Agouti-Related Protein / Q000235:genetics*; D000821:Animal Feed; D000818:Animals; D001066:Appetite / Q000502:physiology*; D001823:Body Composition; D002153:Calorimetry, Indirect / Q000379:methods; D017931:DNA Primers; D002149:Energy Intake; D004734:Energy Metabolism; D005247:Feeding Behavior; D007328:Insulin / Q000097:blood; D000090062:Kruppel-Like Factor 4; D020738:Leptin / Q000097:blood; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D016133:Polymerase Chain Reaction / Q000379:methods; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D014162:Transfection
D054369:Agouti-Related Protein; D017931:DNA Primers; D007328:Insulin; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; D020738:Leptin; D012313:RNA; D008156:Luciferases