Mode of leptin action in chicken hypothalamus.
While there have been many studies in various species examining the mode of central leptin action on food intake, there is however a paucity of data in birds. We have, therefore, addressed this issue in broiler chickens because this strain was selected for high growth rate, hence high food intake. Continuous infusion of recombinant chicken leptin (8 microg/kg/h) during 6 h at a constant rate of 3 ml/h resulted in a significant reduction (49-57%) of food intake in 3-week-old broiler chickens (P < 0.05). The effect of leptin within the central nervous system (CNS) was mediated via selective hypothalamic neuropeptides. Leptin significantly decreased the expression of its receptor (Ob-R), neuropeptide Y (NPY), orexin (ORX), and orexin receptor (ORXR) (P < 0.05), but not that of agouti-related protein (AgRP) (anabolic/orexigenic effectors) in chicken hypothalamus. However, the catabolic/anorexigenic neuropeptides namely proopiomelanocortin (POMC) and corticotropin-releasing hormone (CRH) mRNA levels remained unchanged after leptin treatment. Despite the absence of leptin effect on AgRP (the antagonist of melanocortin receptor MCR) and POMC (the precursor of alpha-melanocyte stimulating hormone which is a potent agonist for MCR), leptin significantly decreased the expression of MCR-4/5 gene in chicken hypothalamus (P < 0.05) suggesting that leptin acts directly (as ligand) or indirectly (via other ligands) on MCRs to regulate food intake in birds. Additionally, leptin down-regulated the expression of fatty acid synthase (FAS) gene in chicken hypothalamus, indicating an additional pathway of leptin action on food intake such as described for FAS inhibitors. These findings provide new insight into the mechanism of leptin control of food intake in chickens.
Dridi
Sami
S
Laboratory of Physiology and Immunology of Domestic Animals, KU Leuven, 3001 Heverlee, Belgium. Sami.Dridi@agr.kuleuven.ac.be
Swennen
Quirine
Q
Decuypere
Eddy
E
Buyse
Johan
J
D054369:Agouti-Related Protein; D000818:Animals; D015139:Blotting, Southern; D002645:Chickens / Q000502:physiology*; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis / Q000187:drug effects; D017931:DNA Primers; D064429:Fatty Acid Synthases / Q000096:biosynthesis / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects*; D007262:Infusions, Intravenous; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects; D020738:Leptin / Q000008:administration & dosage* / Q000097:blood; D009478:Neuropeptide Y / Q000096:biosynthesis / Q000187:drug effects; D009479:Neuropeptides / Q000096:biosynthesis / Q000187:drug effects; D064446:Orexin Receptors; D000068797:Orexins; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis / Q000187:drug effects; D011506:Proteins / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000187:drug effects; D043562:Receptors, G-Protein-Coupled; D054411:Receptors, Leptin; D044101:Receptors, Melanocortin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000187:drug effects; D018013:Receptors, Neuropeptide / Q000096:biosynthesis / Q000187:drug effects; D011994:Recombinant Proteins / Q000008:administration & dosage; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013963:Thyroid Hormones / Q000097:blood
D054369:Agouti-Related Protein; D017931:DNA Primers; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020738:Leptin; D009478:Neuropeptide Y; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D011506:Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D054411:Receptors, Leptin; D044101:Receptors, Melanocortin; D018013:Receptors, Neuropeptide; D011994:Recombinant Proteins; D013963:Thyroid Hormones; D011333:Pro-Opiomelanocortin; D003346:Corticotropin-Releasing Hormone; D064429:Fatty Acid Synthases; D003345:Corticosterone