Effects of nutritional status and gonadal steroids on expression of appetite-regulatory genes in the hypothalamic arcuate nucleus of sheep.
Sheep exhibit photoperiod-driven seasonal changes in appetite and body weight so that nutritional status increases in long days (LD) and decreases in short days (SD); additionally, they are reproductively active in SD and inactive in LD. We addressed the hypothesis that appetite-regulatory genes in the hypothalamus respond differently to changes in nutritional feedback induced by photoperiod as opposed to food restriction, and that responses would be influenced by gonadal steroid status. Castrated oestradiol-implanted male sheep were kept in SD (8 h light/day) or LD (16 h light/day) for 11 weeks, with ad libitum or restricted food (experiment 1; n=8/group). Rams were kept in SD or LD for 12 weeks with ad libitum or restricted food (experiment 2; n=6/group). Gene expression (by in situ hybridisation) in the hypothalamic arcuate nucleus for leptin receptor (OB-Rb), neuropeptide Y (NPY), pro-opiomelanocortin (POMC) and agouti-related peptide (AGRP) was unaffected by photoperiod treatment, but food restriction increased NPY and AGRP mRNAs, in experiment 1. In experiment 2, mRNAs for POMC and cocaine- and amphetamine-regulated transcript (CART) were up-regulated and AGRP down-regulated in SD, while food restriction increased OB-Rb mRNA, increased NPY and AGRP mRNAs only in LD and decreased POMC mRNA only in SD. Thus, gene expression responded differently to photoperiod and food restriction, and the melanocortin pathway was up-regulated in SD in reproductively activated rams but not in oestradiol-implanted castrates. These data support the hypothesis that hypothalamic appetite-regulatory pathways respond differently to changes in nutritional feedback induced by photoperiod as opposed to food restriction, with gonadal steroid feedback additionally influencing the responses.
Archer
Z A
ZA
Energy Balance and Obesity Division, Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK.
Findlay
P A
PA
McMillen
S R
SR
Rhind
S M
SM
Adam
C L
CL
D000728:Androgens / Q000378:metabolism*; D000818:Animals; D001069:Appetite Regulation / Q000502:physiology*; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis; D031204:Caloric Restriction; D004958:Estradiol / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D025461:Feedback, Physiological; D015870:Gene Expression; D017403:In Situ Hybridization / Q000379:methods; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics; D009752:Nutritional Status; D009919:Orchiectomy; D012621:Seasons; D012756:Sheep; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D000728:Androgens; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D009419:Nerve Tissue Proteins; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D004958:Estradiol; D007986:Luteinizing Hormone