Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Diabetes. Jul 15, 2021; 12(7): 1102-1115
Published online Jul 15, 2021. doi: 10.4239/wjd.v12.i7.1102
Decarboxylated osteocalcin, a possible drug for type 2 diabetes, triggers glucose uptake in MG63 cells
Shi Jin, Xiao-Cen Chang, Jing Wen, Jing Yang, Na Ao, Ke-Ying Zhang, Lin-Na Suo, Jian Du
Shi Jin, Xiao-Cen Chang, Jing Wen, Jing Yang, Na Ao, Lin-Na Suo, Jian Du, Department of Endocrinology, The Fourth Affiliated Hospital of China Medical University, Shenyang 110032, Liaoning Province, China
Ke-Ying Zhang, Department of Endocrinology, The Fifth People’s Hospital of Shenyang, Shenyang 110023, Liaoning Province, China
Author contributions: Jin S designed the study, performed the experiments and data analysis, the obtained the funding, and contributed to paper writing; Chang XC and Ao N contributed to obtaining the funding and performed the experiments; Wen J and Yang J contributed to paper writing; Zhang KY and Suo LN performed the data analysis; Du J supervised the project, reviewed and edited the manuscript, and managed the submission process.
Supported by Provincial Science and Technology Department Natural Fund Guidance Project, No. 2019-ZD-0774; National Natural Science Foundation of China, No. 81470998; Liaoning Ministry of Education, No. LQNK201715; and Liaoning Provincial Doctor Start up Fund, No. 20180540008.
Institutional review board statement: Because the objects of this study were cells, not the human beings or animals, the study was not reviewed and approved by any institutional review board.
Conflict-of-interest statement: The authors have no conflicts of interest to declare.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Jian Du, PhD, Professor, Department of Endocrinology, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan Road, Huanggu District, Shenyang 110032, Liaoning Province, China. dujian_1962@163.com
Received: January 21, 2021
Peer-review started: January 21, 2021
First decision: March 16, 2021
Revised: April 5, 2021
Accepted: June 4, 2021
Article in press: June 4, 2021
Published online: July 15, 2021
Processing time: 171 Days and 19 Hours
ARTICLE HIGHLIGHTS
Research background

Uncarboxylated osteocalcin (GluOC) has been reported to improve glucose metabolism, prevent type 2 diabetes, and decrease the severity of obesity in mice with type 2 diabetes. GluOC can increase glucose uptake in a variety of cells. GluOC has great potential to become a new drug for the treatment of type 2 diabetes in the future.

Research motivation

Glucose metabolism is the main source of energy for osteoblast proliferation and differentiation. However, both the direct effects of GluOC on glucose uptake in bone tissues and the underlying mechanisms remain unexplored.

Research objectives

To investigate the effects of decarboxylated osteocalcin (dcOC), a kind of GluOC, on glucose uptake in human osteoblast-like osteosarcoma cells and the possible signaling pathways involved.

Research methods

MG63 cells (human osteoblast-like osteosarcoma cells) were treated with dcOC (0, 0.3, 3, 10, or 30 ng/mL) for 1 and 72 h, and glucose uptake was measured by flow cytometry. The effect of dcOC on cell proliferation was measured with a CCK-8 assay, and alkaline phosphatase (ALP) enzyme activity was measured. PI3K was inhibited with LY294002, and hypoxia-inducible factor 1 alpha (HIF-1α) was silenced with siRNA. Then, the G protein-coupled receptor family C group 6 subtype A, total Akt, phosphorylated Akt, HIF-1α, and glucose transporter 1 (GLUT1) levels were measured by Western blot to elucidate the possible pathways by which dcOC modulates glucose uptake.

Research results

The glucose uptake of MG63 cells was significantly increased compared with that of the paired control cells after short-term (1 h) treatment and long-term (72 h) treatment with dcOC at different concentrations. LY294002 abolished the dcOC-mediated (1 h) promotion of Akt phosphorylation and glucose uptake without affecting GLUT1 protein expression. Long-term dcOC stimulation triggered Akt phosphorylation and increased the protein levels of HIF-1α, GLUT1, and Runx2 in a dose-dependent manner. Inhibition of HIF-1α abolished the dcOC-mediated glucose uptake and substantially decreased GLUT1 protein expression. DcOC intervention promoted cell proliferation in a time- and dose-dependent manner. Treatment with dcOC affected the ALP activity in MG63 cells.

Research conclusions

DcOC can promote glucose uptake in MG63 cells in vitro. DcOC may affect the invasion and migration of MG63 cells and the prognosis of osteosarcoma patients by affecting ALP activity and Runx2 expression.

Research perspectives

DcOC can promote glucose uptake in human osteoblast-like osteosarcoma cells. It is necessary to be aware of its possible adverse effects on osteoblastic osteosarcoma while considering dcOC as a potential treatment for type 2 diabetes.