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Life Sci. 2013 Mar 21;92(10):533-40. doi: 10.1016/j.lfs.2013.01.001. Epub 2013 Jan 25.

Exendin-4 increases bone mineral density in type 2 diabetic OLETF rats potentially through the down-regulation of SOST/sclerostin in osteocytes.

Author information

1
Imaging Science based Lung and Bone Disease Research Center, Wonkwang University, Iksan, Jeonbuk, Republic of Korea.

Abstract

AIM:

Glucagon-like peptide-1 (GLP-1) receptor participates in the control of bone resorption in GLP-1 knockout mice. Also, GLP-1 induces an insulin- and parathyroid hormone-independent osteogenic action through osteoclasts and osteoblasts in insulin-resistant and type 2 diabetic rats. Osteocytes are now considered central to bone homeostasis. A secreted product of osteocytes, sclerostin, inhibits bone formation. However, the effect of GLP-1 on osteocytes remains unclear. Therefore, we investigated the effect of GLP-1 on bone mineral density (BMD), and the cellular and molecular mechanisms associated with osteocytes.

MAIN METHODS:

We investigated the presence of GLP-1 receptors in osteocyte-like MLO-Y4 cells and osteocytes of rat femurs through RT-PCR, Western blot and confocal microscopy, and investigated the effect of exendin-4 on the expression of mRNA (by quantitative real-time RT-PCR) and protein (by Western blot) of SOST/sclerostin in osteocyte-like MLO-Y4 cells during culture under normal or high-glucose (30 mM) conditions, and measured circulating levels of sclerostin, osteocalcin, and tartrate-resistant alkaline phosphatase (TRAP) 5b and femoral BMD in type 2 diabetic OLETF rats treated with exendin-4.

KEY FINDINGS:

GLP-1 receptor was present on MLO-Y4 cells and osteocytes of rat femurs. Exendin-4 reduced the mRNA expression and protein production of SOST/sclerostin under normal or high-glucose conditions in MLO-Y4 cells. Exendin-4 reduced serum levels of sclerostin, increased serum levels of osteocalcin, and increased femoral BMD in type 2 diabetic OLETF rats.

SIGNIFICANCE:

These findings suggest that exendin-4 might increase BMD by decreasing the expression of SOST/sclerostin in osteocytes in type 2 diabetes.

PMID:
23357248
DOI:
10.1016/j.lfs.2013.01.001
[Indexed for MEDLINE]

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