Growth-stimulating neuropeptides and the innate immune system

The manipulation of the growth characteristics of aquatic organisms constitutes a high priority for the biotechnological industry, given the expected worldwide increase in food demand and the current food shortages, especially in animal protein, for significant segments of the population. The stimulation of growth, aimed at reducing the extension of harvest cycles for aquaculture and at decreasing the high mortality typical of larval stages in fish; as well as the use of immunostimulants to allow aquacultural populations to cope with the conditions of intensive culture, are two of the main targets of modern aquacultural biotechnology. Recent data about the immuneendocrine connection in fish have shown that growth hormone has a stimulatory effect on several parameters of the innate immune system. Therefore, the use of biotechnological means for the stimulation of growth hormone and, consequently, the innate immune system, is a promising mean for fulfilling this goal. The present work summarizes our study of the influence of the pituitary adenylate cyclase-activating peptide (PACAP) and the PACAPrelated peptide (PRP) from Clarias gariepinus, as well as neuropeptide Y from Oreochromis sp. on the growth characteristics and innate immune system of fish. The results show that these neuropeptides not only have growthpromoting and development-related effects, but also stimulate several elements of the innate immune response such as lysozyme, lectins, nitric oxide and anti-oxidative defenses (catalase, superoxide dismutase and reduced glutathione levels).