Study summary · research use only
The influence of ghrelin agonist ipamorelin acetate on the hypothalamic-pituitary-testicular axis in a cichlid fish, Oreochromis mossambicus
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This study in the cichlid fish Oreochromis mossambicus (tilapia) examined effects of ipamorelin acetate (IPA), a ghrelin agonist, on the hypothalamic-pituitary-testicular axis. Administration of 5 or 30 µg of IPA for 21 days produced a dose-dependent rise in food intake along with increased numbers of primary spermatocytes, secondary spermatocytes, and early spermatids compared with controls; fish given 30 µg IPA also showed increased late spermatids and lobule/lumen area. GnRH-immunoreactive fibre percentage in the hypothalamus and anterior pituitary did not differ significantly across groups, but androgen receptor protein expression was elevated with 30 µg IPA. Serum LH and 11-ketotestosterone (11-KT) were elevated with either 5 or 30 µg of IPA compared with controls, which the authors suggest reflects effects on germ cell development mediated via 11-KT, androgen receptors, and LH.
Abstract
Ghrelin, a peptide found in the brain and gut, is predicted to play a significant role in the control of various physiological systems in fish. The objective of this study was to examine the impact of ipamorelin acetate (IPA), a ghrelin agonist, on the reproductive axis of the tilapia Oreochromis mossambicus. The administration of either 5 or 30 µg of IPA for 21 days led to a significant and dose-dependent rise in food intake concomitant with a significant increase in the numbers of primary spermatocytes, secondary spermatocytes, and early spermatids compared to the control group. There was a significant rise in the number of late spermatids, as well as the areas of the lobule and lumen, in fish treated with 30 µg of IPA, compared to the control group. Moreover, there was no significant difference in the percentage of gonadotropin-releasing hormone (GnRH)-immunoreactive fibres in the hypothalamus and anterior pituitary gland across different groups. However, a significant elevation in the expression of androgen receptor protein was observed in fish treated with 30 µg of IPA. Furthermore, the concentrations of luteinizing hormone (LH) and 11-ketotestosterone (11-KT) in the serum of fish treated with either 5 or 30 µg of IPA were significantly elevated in comparison to the control group. Collectively, these findings suggest that the administration of ghrelin enhances the development of germ cells during the meiosis-I phase and that this effect might be mediated via the stimulation of 11-KT and androgen receptors at the testicular level and LH at the pituitary level in the tilapia.
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