Circadian expression of genes regulating food intake.
OBJECTIVE
The Agouti-related protein (AgRP), neuropeptide Y (NPY), proopiomelanocortin (POMC), cocaine and amphetamine-regulated transcript (CART), Orexin, melanin concentrating hormone (MCH), leptin, and its hypothalamic receptor (LR) are key regulators of food intake and energy homeostasis. In the present study, we examined the circadian expression profiles of these genes.


METHODS
We used quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to measure mRNA levels, spectral analysis to evaluate periodicity, and correlation analysis to examine for associations with diurnal food intake.


RESULTS
No gene in particular stood out as a strong candidate, but the overall circadian expression profiles of leptin and its hypothalamic receptor came close to statistically and graphically resembling the diurnal feeding behavior of mice. In mathematical terms, adrenal AgRP exhibited strong circadian expression and had the highest correlation with food intake, followed by leptin. Yet its highest point of expression occurred 8 hours after nocturnal food intake had peaked, suggesting that adrenal AgRP could not play a direct role in the initiation of nocturnal feeding; neither did hypothalamic AgRP, NPY, POMC, CART, Orexin, or MCH.


CONCLUSIONS
These data show that ad libitum feeding in mice is influenced by complex central and peripheral circuits involving orexigenic and anorectic agents of which leptin and its hypothalamic receptor could play more prevalent roles.
Stütz
Adrian M
AM
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
Staszkiewicz
Jaroslaw
J
Ptitsyn
Andrey
A
Argyropoulos
George
G
D000311:Adrenal Glands / Q000378:metabolism; D054369:Agouti-Related Protein; D000818:Animals; D001069:Appetite Regulation / Q000235:genetics*; D002940:Circadian Rhythm / Q000502:physiology*; D005786:Gene Expression Regulation; D007028:Hypothalamic Hormones / Q000235:genetics / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D020738:Leptin / Q000235:genetics / Q000378:metabolism; D008297:Male; D008543:Melanins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009478:Neuropeptide Y / Q000235:genetics / Q000378:metabolism; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D000068797:Orexins; D010907:Pituitary Hormones / Q000235:genetics / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D054411:Receptors, Leptin; D013737:Testis / Q000378:metabolism; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D054369:Agouti-Related Protein; C515199:Agrp protein, mouse; D007028:Hypothalamic Hormones; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020738:Leptin; D008543:Melanins; D009419:Nerve Tissue Proteins; D009478:Neuropeptide Y; D009479:Neuropeptides; D000068797:Orexins; D010907:Pituitary Hormones; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D011333:Pro-Opiomelanocortin; C019463:melanin-concentrating hormone