Jithine Jayakumar Rajeswari1, Emilio J Vélez1, Suraj Unniappan2. 1. Laboratory of Integrative Neuroendocrinology, Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, S7N 5B4, Canada. 2. Laboratory of Integrative Neuroendocrinology, Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, S7N 5B4, Canada. Electronic address: suraj.unniappan@usask.ca.
Abstract
OBJECTIVE: Phoenixin-20 (Pnx-20) is a bioactive peptide with endocrine-like actions in vertebrates. Recent studies suggest Pnx-20 promotes growth hormone/insulin-like growth factors (Gh/Igf) axis, an important endocrine regulator of growth in mammals and fish. DESIGN: In this research, we determined whether Pnx-20 affects the different members of the Igf family, its binding proteins and receptors (Igf-system) in zebrafish liver and muscle. RESULTS: In vivo administration of Pnx-20 downregulated igfs, igf receptors (igfrs) and igf binding protein (igfbp) 5 mRNA expression in the liver of male and female zebrafish at both 1 and 6 h post-intraperitoneal (IP) injection. Interestingly, this effect occurred at a relatively earlier timepoint in female zebrafish suggesting sex-specific differences in Pnx-20 action. Besides, either 6 or 24 h in vitro incubations with Pnx-20 downregulated the expression of all igfs, igfrs and igfbp5 mRNAs (except igf2a) analyzed in a zebrafish liver cell (ZFL) line. Moreover, siRNA-mediated knockdown of Pnx-20 upregulated all Igf-system mRNAs analyzed in ZFL cells. Together, these results (both in vivo and in vitro) revealed a general suppressive action for both endogenous and exogenous Pnx-20 on the hepatic Igf-system of zebrafish. In contrast, a general sex-specific upregulation of the Igf-system mRNAs analyzed was found in the muscle of Pnx-20 injected fish. Future research should explore the sex- and time-differences observed in the present study. CONCLUSIONS: Collectively, this research shows that Pnx-20 is a tissue-specific regulator of the liver (suppressor) and muscle (stimulant) Igf signaling in both male and female zebrafish.
OBJECTIVE: Phoenixin-20 (Pnx-20) is a bioactive peptide with endocrine-like actions in vertebrates. Recent studies suggest Pnx-20 promotes growth hormone/insulin-like growth factors (Gh/Igf) axis, an important endocrine regulator of growth in mammals and fish. DESIGN: In this research, we determined whether Pnx-20 affects the different members of the Igf family, its binding proteins and receptors (Igf-system) in zebrafish liver and muscle. RESULTS: In vivo administration of Pnx-20 downregulated igfs, igf receptors (igfrs) and igf binding protein (igfbp) 5 mRNA expression in the liver of male and female zebrafish at both 1 and 6 h post-intraperitoneal (IP) injection. Interestingly, this effect occurred at a relatively earlier timepoint in female zebrafish suggesting sex-specific differences in Pnx-20 action. Besides, either 6 or 24 h in vitro incubations with Pnx-20 downregulated the expression of all igfs, igfrs and igfbp5 mRNAs (except igf2a) analyzed in a zebrafish liver cell (ZFL) line. Moreover, siRNA-mediated knockdown of Pnx-20 upregulated all Igf-system mRNAs analyzed in ZFL cells. Together, these results (both in vivo and in vitro) revealed a general suppressive action for both endogenous and exogenous Pnx-20 on the hepatic Igf-system of zebrafish. In contrast, a general sex-specific upregulation of the Igf-system mRNAs analyzed was found in the muscle of Pnx-20 injected fish. Future research should explore the sex- and time-differences observed in the present study. CONCLUSIONS: Collectively, this research shows that Pnx-20 is a tissue-specific regulator of the liver (suppressor) and muscle (stimulant) Igf signaling in both male and female zebrafish.