Synthetic Growth Hormone Secretagogue GHRP-6 Exhibits Enhanced Growth Activity and Immune System Stimulation in Teleost Fish and Shrimp
Keywords:
Growth Hormone, Secretagogues, Peptides, Larvae, growth, Innate Immune stateAbstract
Aquaculture is part of the solution for meeting the growing world demand for food, mainly as an animal
protein source. However, current yields are insufficient for aquaculture to play this crucial role. Growth-rate
enhancement is one of the approaches that have been exploited in this regard. Also, losses caused by bacteria,
viruses and parasites remain a significant problem. It has been demonstrated that growth stimulants contribute
not only to growth enhancement but also to fish health improvement. Growth Hormone Releasing Peptide-6
(GHRP-6) is one of the earliest-developed, synthetic, peptidyl growth hormone secretagogue receptor
agonists. These compounds mimic the effect of the endogenous ligand, ghrelin. This peptide has shown its
benefits for both growth enhancement and immune system stimulation in fish and crustaceans. In the present
study, we demonstrate that intraperitoneal administration of GHRP-6 induces liver insulin growth factor-I
messenger RNA, and increases growth hormone levels in juvenile tilapia (Oreochromis sp.), in a time-course
experiment. In addition, administration of GHRP-6 in formulated feed to tilapia larvae was assessed. Growth
and immune parameters such as lectin titers and intestinal intraepithelial lymphocyte numbers were increased
in treated larvae. We also evaluated the effect of GHRP-6 injection over feed intake in shrimp and its effects
on shrimp growth when the peptide was administrated by successive immersion baths. GHRP-6 increased
feed intake, body weight and size, the number of rostral spines and gill branches, protein concentration and
haemocyte number in treated shrimps.
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