Inhibition of the canonical Wnt pathway by high glucose can be reversed by parathyroid hormone-related protein in osteoblastic cells

Authors

  • Ana López-Herradón,

    1. Laboratorio de Metabolismo Mineral y Óseo, Instituto de Investigación Sanitaria (IIS)-Fundación Jiménez Díaz and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
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  • Sergio Portal-Núñez,

    1. Laboratorio de Metabolismo Mineral y Óseo, Instituto de Investigación Sanitaria (IIS)-Fundación Jiménez Díaz and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
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  • Adela García-Martín,

    1. Laboratorio de Metabolismo Mineral y Óseo, Instituto de Investigación Sanitaria (IIS)-Fundación Jiménez Díaz and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
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  • Daniel Lozano,

    1. Laboratorio de Metabolismo Mineral y Óseo, Instituto de Investigación Sanitaria (IIS)-Fundación Jiménez Díaz and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
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  • Francisco C. Pérez-Martínez,

    1. NanoDrugs, S.L., Parque Científico y Tecnológico, Albacete, Spain
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  • Valentín Ceña,

    1. CIBERNED, Instituto de Salud Carlos III, Madrid, Spain
    2. Unidad Asociada Neurodeath, Departamento de Ciencias Médicas, CSIC-Universidad de Castilla-La Mancha, Albacete, Spain
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  • Pedro Esbrit

    Corresponding author
    1. Laboratorio de Metabolismo Mineral y Óseo, Instituto de Investigación Sanitaria (IIS)-Fundación Jiménez Díaz and Red Temática de Investigación Cooperativa en Envejecimiento y Fragilidad (RETICEF), Madrid, Spain
    • Laboratorio de Metabolismo Mineral y Óseo, Instituto de Investigación Sanitaria (IIS)-Fundación Jiménez Díaz, Avda. Reyes Católicos, 2, 28040 Madrid, Spain.
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  • The authors have declared that no competing interests exist.

Abstract

Recent in vivo findings suggest that the bone sparing effect of parathyroid hormone-related protein (PTHrP) in diabetic mice might occur at least in part through targeting a suppressed Wnt/β-catenin pathway in osteoblasts. We here aimed to examine the inhibitory action of a high glucose environment on specific components of the canonical Wnt pathway, and the putative compensatory effects of PTHrP, in osteoblastic cell cultures. Mouse osteoblastic MC3T3-E1 cells and primary cultures of fetal mouse calvaria were exposed to normal (5.5 mM) or high (25 mM) D-glucose (HG), with or without PTHrP (1–36) or PTHrP (107–139) for different times. In some experiments, MC3T3-E1 cells were incubated with the Wnt pathway activators Wnt3a and LiCl, or were transfected with plasmids encoding either a mutated β-catenin that cannot be targeted for degradation or a human PTHrP (−36/+139) cDNA, or the corresponding empty plasmid, in the presence or absence of HG. The gene expression of Wnt3a and low density receptor-like proteins (LRP)-5 and 6, as well as β-catenin protein stabilization and β-catenin-dependent transcription activity were evaluated. Oxidative stress status under HG condition was also assessed. The present data demonstrate that HG can target different components of the canonical Wnt pathway, while β-catenin degradation appears to be a key event leading to inhibition of Wnt/β-catenin signaling in mouse osteoblastic cells. Both PTHrP peptides tested were able to counteract this deleterious action of HG. These in vitro findings also provide new clues to understand the underlying mechanisms whereby PTHrP can increase bone formation. J. Cell. Biochem. 114: 1908–1916, 2013. © 2013 Wiley Periodicals, Inc.

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