How many *feeding* peptides are there?
Ghrelin Regulates Feeding in Rats
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WESTPORT, CT (Reuters Health) Jan 11 - The acylated peptide ghrelin regulates feeding in rats, Japanese researchers report in the January 11th issue of Nature. They conclude that ghrelin is a "mediator of feeding, and probably has a function in growth regulation by stimulating feeding and release of growth hormone."
To look at the effect of ghrelin on feeding, Dr. Masamitsu Nakazato, from Miyazaki Medical College, in Kiyotake, and colleagues injected the peptide intracerebroventricularly into rats. They found that ghrelin increased food intake under either satiated or feeding conditions.
An antibody to ghrelin suppressed starvation-induced feeding and free feeding. Although ghrelin stimulates growth hormone release, it was effective in stimulating food intake even in rats with a disrupted growth hormone gene.
Next, the researchers determined which neurons were being activated after administration of ghrelin. They found that activated neurons were primarily in areas associated with the regulation of feeding, including neuropeptide Y neurons and agouti-related protein neurons in the arcuate nucleus.
Blocking neuropeptide Y or agouti-related protein with antibodies or antagonists abolished ghrelin-induced feeding. However, leptin blocked ghrelin-induced feeding, and ghrelin blocked the leptin-induced reduction of feeding, suggesting that "ghrelin may antagonize leptin action in the regulation of the neuropeptide Y system."
"Further investigations of ghrelin's function will help our understanding of physiological feeding mechanisms," Dr. Nakazato's group concludes, "and should facilitate the study of eating disorders."
Nature 2001;409:194-197. |
