Differential roles for octanoylated and decanoylated ghrelins in regulating appetite and metabolism.

Since its identification in 1999, ghrelin has been identified in all vertebrate groups. The "active core" of ghrelin is highly conserved among vertebrates, suggesting its biological activity to be also conserved. In fish, both acylated forms of ghrelin have been identified; however, the ratio of the ghrelin-C8 to ghrelin-C10 is not as great as observed in mammals.

Glucose regulates ghrelin, neuropeptide Y, and the GH/IGF-I axis in the tilapia, Oreochromis mossambicus.

In general, a fish's ability to clear glucose is sluggish in relation to mammals, which has lead to the idea that fish are glucose intolerant. It has been reported that circulating glucose levels do fluctuate in response to environmental challenges. Recent reports suggest that glucose may function as a metabolic signal regulating 'glucosensors' in the brain in fish, as has been reported in mammals.