Leptin regulates appetite-related neuropeptides in the hypothalamus of developing rats without affecting food intake.
Leptin regulates food intake in adult mammals by stimulating hypothalamic anorexigenic pathways and inhibiting orexigenic ones. In developing rodents, fat stores are low, yet circulating leptin levels are high and do not appear to regulate food intake. We determined whether two appetite-related neuropeptides [neuropeptide Y (NPY) and proopiomelanocortin (POMC)] and food intake behavior are sensitive to leptin [3 mg/kg body weight (BW), ip] in neonates. We measured the effects of 1) acute leptin administration (3 mg/kg BW, ip, 3 h before testing) on food intake on postnatal day (PND) 5, 8, and 10; and 2) chronic leptin treatment (3 mg/kg BW, ip, daily PND3-PND10) on BW gain and fat pads weight on PND10. In addition to hypothalamic POMC and NPY expression, we determined the expression of suppressor of cytokine signaling-3, all subtypes of leptin receptors, and corticotropin-releasing factor receptor-2 mRNA in PND10 pups receiving either an acute (PND10) or a chronic (PND 3-10) leptin (3 mg/kg BW, ip) or vehicle treatment. Brains were removed 30 or 120 min after the last injection. Acute leptin administration did not affect food intake at any age tested. Chronic leptin treatment did not change BW but decreased fat pad weight significantly. In the arcuate nucleus (ARC), acute leptin increased SOCS-3 and POMC mRNA levels, but decreased NPY mRNA levels in the rostral part of ARC. Chronic leptin down-regulated all subtypes of leptin receptors mRNA and decreased NPY mRNA levels in the caudal ARC but had no further effect on POMC expression. Chronic leptin increased corticotropin-releasing factor receptor-2 mRNA levels in the ventromedial hypothalamus. We conclude that despite adult-like effects of leptin on POMC, NPY, and CRFR-2 expression in neonates, leptin does not regulate food intake during early development.
Proulx
Karine
K
McGill University, Department of Psychiatry, Douglas Hospital Research Center, Montréal, Québec, Canada H4H 1R3.
Richard
Denis
D
Walker
Claire-Dominique
CD
D000273:Adipose Tissue / Q000254:growth & development; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D001066:Appetite / Q000502:physiology*; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism; D004435:Eating / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D007031:Hypothalamus / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000378:metabolism; D020738:Leptin / Q000008:administration & dosage / Q000494:pharmacology*; D009478:Neuropeptide Y / Q000235:genetics; D009479:Neuropeptides / Q000235:genetics*; D009929:Organ Size / Q000187:drug effects; D011333:Pro-Opiomelanocortin / Q000235:genetics; D011506:Proteins / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000235:genetics; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics; D054411:Receptors, Leptin; D012097:Repressor Proteins; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D015430:Weight Gain / Q000187:drug effects
D020738:Leptin; D009478:Neuropeptide Y; D009479:Neuropeptides; D011506:Proteins; D011956:Receptors, Cell Surface; D018019:Receptors, Corticotropin-Releasing Hormone; D054411:Receptors, Leptin; D012097:Repressor Proteins; C491410:Socs3 protein, rat; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D011333:Pro-Opiomelanocortin