Hypothalamic control of photoperiod-induced cycles in food intake, body weight, and metabolic hormones in rams.
This study used a hypothalamo-pituitary disconnected (HPD) sheep model to investigate the central regulation of long-term cycles in voluntary food intake (VFI) and body weight (BW). VFI, BW, and circulating concentrations of metabolic hormones [alpha-melanocyte-stimulating hormone (alpha-MSH), insulin-like growth factor-1 (IGF-1), insulin, and leptin] were measured in HPD and control Soay rams exposed to alternating 16 weekly periods of long and short days for 80 wk. In the controls, the physiology was cyclical with a 32-wk periodicity corresponding to the lighting regimen. VFI and BW increased under long days to a maximum early into short days, and there were associated increases in blood concentrations of alpha-MSH, insulin, and leptin. In the HPD rams, there were no significant photoperiod-induced changes in any of the parameters. VFI increased after surgery for 8 wk and then gradually declined, although BW increased progressively and the HPD rams became obese. Concentrations of alpha-MSH, insulin, and leptin in peripheral blood were permanently increased (>200%), and levels of IGF-1 decreased (<55%). The HPD lesion effectively destroyed the entire median eminence [no nerve terminals immunostained for tyrosine hydroxylase (TH) and gonadotropin-releasing hormone] and the adjacent arcuate nucleus (no perikarya immunostained for proopiomelanocortin or TH, and no cells expressed neuropeptide Y mRNA). The results support the conclusion that arcuate hypothalamic systems generate long-term rhythms in VFI, BW, and energy balance.
Lincoln
G A
GA
Medical Research Council Human Reproductive Sciences Unit, Centre for Reproductive Biology, Edinburgh EH3 9ET, United Kingdom.
Rhind
S M
SM
Pompolo
S
S
Clarke
I J
IJ
D000222:Adaptation, Physiological / Q000502:physiology; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001066:Appetite / Q000502:physiology; D001111:Arcuate Nucleus of Hypothalamus / Q000737:chemistry / Q000502:physiology; D001835:Body Weight / Q000502:physiology*; D003714:Denervation; D004435:Eating / Q000502:physiology*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D005947:Glucose / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis; D007004:Hypoglycemic Agents / Q000097:blood / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000737:chemistry / Q000502:physiology* / Q000601:surgery; D007150:Immunohistochemistry; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000097:blood; D008297:Male; D009478:Neuropeptide Y / Q000032:analysis / Q000235:genetics; D009765:Obesity / Q000378:metabolism; D017440:Photoperiod; D011333:Pro-Opiomelanocortin / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D012621:Seasons; D012756:Sheep; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis; D000521:alpha-MSH / Q000097:blood*
D007004:Hypoglycemic Agents; D007328:Insulin; D020738:Leptin; D009478:Neuropeptide Y; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D000521:alpha-MSH; D011333:Pro-Opiomelanocortin; D007334:Insulin-Like Growth Factor I; D014446:Tyrosine 3-Monooxygenase; D005947:Glucose