Transcriptional and pathway analysis in the hypothalamus of newly hatched chicks during fasting and delayed feeding.
BACKGROUND
The hypothalamus plays a central role in regulating appetite and metabolism. However, the gene networks within the hypothalamus that regulate feed intake and metabolism, and the effects of fasting on those pathways are not completely understood in any species. The present experiment evaluated global hypothalamic gene expression in newly hatched chicks using microarray analysis to elucidate genes and pathways regulated by feeding, fasting, and delayed feeding. Ten groups of chicks were sampled over four days post-hatch, including fed, fasted, and 48 h fasted followed by access to feed for 4 h, 24 h, and 48 h. Hypothalamic samples were collected for microarray analysis (n = 4). Expression patterns of selected genes were confirmed by quantitative real-time PCR. Pathway analysis of the microarray results predicted a network of genes involved in neuropeptide or neurotransmitter signaling. To confirm the functionality of this predicted gene network, hypothalamic neurons from fed and fasted chicks were isolated and cultured in the presence of neuropeptide Y, somatostatin, alpha-melanocyte stimulating hormone, norepinephrine, and L-phospho-serine. Results confirmed functional relationships among members of the predicted gene network. Moreover, the effects observed were dependent upon the nutritional state of the animals (fed vs. fasted).


RESULTS
Differences in gene expression (> or = 1.6 fold) were detected in 1,272 genes between treatments, and of those, 119 genes were significantly (P < 0.05) different. Pathway Miner analysis revealed that six genes (SSTR5, NPY5R, POMC, ADRB2, GRM8, and RLN3) were associated within a gene network. In vitro experiments with primary hypothalamic neurons confirmed that receptor agonists involved in this network regulated expression of other genes in the predicted network, and this regulation within the network was influenced by the nutritional status and age of the chick.


CONCLUSIONS
Microarray analysis of the hypothalamus during different nutritional states revealed that many genes are differentially regulated. We found that functional interactions exist among six differentially regulated genes associated within a putative gene network from this experiment. Considering that POMC, an important gene in controlling metabolism, was central to this network, this gene network may play an important role in regulation of feeding and metabolism in birds.
Higgins
Stacy E
SE
Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA.
Ellestad
Laura E
LE
Trakooljul
Nares
N
McCarthy
Fiona
F
Saliba
Jason
J
Cogburn
Larry A
LA
Porter
Tom E
TE
D000367:Age Factors; D000818:Animals; D002478:Cells, Cultured; D002645:Chickens / Q000235:genetics / Q000502:physiology; D004435:Eating / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D053263:Gene Regulatory Networks; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000378:metabolism; D009752:Nutritional Status; D020411:Oligonucleotide Array Sequence Analysis