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Int J Mol Med. 2014 Aug;34(2):475-82. doi: 10.3892/ijmm.2014.1787. Epub 2014 May 27.

Expression of glucagon-like peptide-1 receptor and glucose‑dependent insulinotropic polypeptide receptor is regulated by the glucose concentration in mouse osteoblastic MC3T3-E1 cells.

Author information

1
Department of Orthodontic Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo 113-8549, Japan.
2
Department of Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo 113-8549, Japan.

Abstract

Glucose-dependent insulinotropic polypeptide receptor (GIPR) and glucagon-like peptide-1 receptor (GLP‑1R) are incretin receptors that play important roles in regulating insulin secretion from pancreatic β cells. Incretin receptors are also thought to play a potential role in bone metabolism. Osteoblasts in animals and humans express GIPR; however, the presence of GLP-1R in these cells has not been reported to date. Thus, the aim of this study was to determine whether GLP-1R and GIPR are expressed in osteoblastic cells, and whether their expression levels are regulated by the extracellular glucose concentration. Mouse osteoblastic MC3T3-E1 cells were cultured in medium containing normal (5.6 mM) or high (10, 20 or 30 mM) glucose concentrations, with or without bone morphogenetic protein-2 (BMP-2). RT-PCR, western blot analysis and immunofluorescence were carried out to determine GIPR and GLP-1R mRNA and protein expression levels. Cell proliferation was also assessed. The GLP-1R and GIPR mRNA expression levels were higher in the MC3T3-E1 cells cultured in medium containing high glucose concentrations with BMP-2 compared with the cells cultured in medium containing normal glucose concentrations with or without BMP-2. GLP-1R protein expression increased following culture in high-glucose medium with BMP-2 compared with culture under normal glucose conditions. However, the cellular localization of GLP-1R was not affected by either glucose or BMP-2. In conclusion, our data demonstrate that the expression of GLP-1R and GIPR is regulated by glucose concentrations in MC3T3-E1 cells undergoing differentiation induced by BMP-2. Our results reveal the potential role of incretins in bone metabolism.

PMID:
24866833
DOI:
10.3892/ijmm.2014.1787
[Indexed for MEDLINE]

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