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Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats

Authors
 Junghun Lee  ;  Ahreum Kwon  ;  Hyun Wook Chae  ;  Woo Jung Lee  ;  Tae Hyuk Kim  ;  Ho-Seong Kim 
Citation
 YONSEI MEDICAL JOURNAL, Vol.59(10) : 1174-1180, 2018 
Journal Title
 YONSEI MEDICAL JOURNAL 
ISSN
 0513-5796 
Issue Date
2018
Keywords
Growth hormone-releasing peptide ; growth ; oral administration ; rats ; somatostatin
Abstract
PURPOSE: Growth hormone secretagogues (GHSs) possess the ability to release growth hormone (GH) in the body. This study aimed to investigate the effects of MK-677, an orally active GHS, on somatic growth in rats. MATERIALS AND METHODS: The serum levels of GH were measured after oral administration of MK-677 to confirm GH stimulatory effects. Body weight, body length, tibia length, epiphyseal plate width, and serum levels of insulin-like growth factor (IGF)-I were measured after oral administration of 4 mg/kg of MK-677 for 6 weeks to investigate growth-promoting effects. RESULTS: Oral administration of MK-677 at 4 mg/kg increased peak GH concentrations by 1.8-fold, compared to baseline. However, oral administration of MK-677 for 6 weeks did not increase body growth or serum levels of IGF-I. At 6 weeks after treatment, the GH response to MK-677 was abolished. Pituitary GH mRNA and hypothalamic GH-releasing hormone mRNA, and GH secretagogue receptor (GHSR) mRNA expression in the pituitary and hypothalamus did not differ between the control and treatment group. Somatostatin (SST) mRNA expression in the hypothalamus was markedly increased in the treatment group, whereas SST receptor (SSTR)-2 mRNA expression in the pituitary gland was decreased. Protein expression of hypothalamic GHSR, SST, and pituitary SSTR-2 showed patterns similar to those for mRNA expression. CONCLUSION: Our results suggest that prolonged administration of MK-677 in rats does not promote growth despite the GH stimulatory effect of MK-677, which may be related to increased expression of SST in the hypothalamus. Further studies are needed to overcome the observed desensitization to GHS.
Files in This Item:
T201804447.pdf Download
DOI
10.3349/ymj.2018.59.10.1174
Appears in Collections:
1. College of Medicine (의과대학) > Dept. of Pediatrics (소아청소년과학교실) > 1. Journal Papers
Yonsei Authors
Kwon, Ah Reum(권아름) ORCID logo https://orcid.org/0000-0002-9692-2135
Kim, Ho Seong(김호성) ORCID logo https://orcid.org/0000-0003-1135-099X
Chae, Hyun Wook(채현욱) ORCID logo https://orcid.org/0000-0001-5016-8539
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/166674
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