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Endocrine. 2018 Mar;59(3):622-632. doi: 10.1007/s12020-017-1396-0. Epub 2017 Sep 2.

Insulin and osteocalcin: further evidence for a mutual cross-talk.

Author information

1
Department of Health Sciences, University "Magna Græcia" of Catanzaro, Viale Europa (Località Germaneto), 88100, Catanzaro, Italy.
2
Laboratory of Molecular Genetics, The Institute of Medical Science, University of Tokyo, 108-8639, Tokyo, Japan.
3
Department of Health Sciences, University "Magna Græcia" of Catanzaro, Viale Europa (Località Germaneto), 88100, Catanzaro, Italy. brunetti@unicz.it.

Abstract

PURPOSE:

In the last few years, bone has been recognized as an endocrine organ that modulates glucose metabolism by secretion of osteocalcin, an osteoblast-specific hormone, that influences fat deposition and blood sugar levels. To date, however, very few in vitro models have been developed to investigate, at the molecular levels, the relationship between glucose, insulin and osteocalcin. This study aims at covering this gap.

METHODS:

We studied osteogenic differentiation, osteocalcin gene expression, and osteblast-mediated insulin secretion, using cultured MG-63 human osteoblast-like cells that underwent glucotoxicity and insulin resistance. In addition, we investigated whether a correlation existed between hyperglycemia and/or insulin resistance and total osteocalcin serum concentrations in patients.

RESULTS:

While insulin and low glucose increased osteocalcin gene expression, disruption of insulin signaling in MG-63 osteoblasts and high glucose concentration in cell culture medium decreased osteocalcin gene transcription and reduced osteogenic differentiation. Concomitantly, insulin secretion was significantly impaired in rat INS-1 β-cells treated with conditioned medium from insulin resistant MG-63 cells or cells exposed to high glucose concentrations. Also, chronic hyperglycemia, but not insulin resistance, inversely correlated with circulating osteocalcin levels in patients.

CONCLUSION:

Our results further support the existence of an endocrine axis between bone, where osteocalcin is produced, and pancreatic β-cells, and add new insights into the molecular details of this relationship. These findings may contribute to the understanding of osteocalcin regulation and its role in metabolism.

KEYWORDS:

Bone; Insulin action; Osteocalcin; Type 2 diabetes

PMID:
28866834
PMCID:
PMC5847166
DOI:
10.1007/s12020-017-1396-0
[Indexed for MEDLINE]
Free PMC Article

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