PKM2 is a Novel Osteoporosis-Associated Protein in Chinese

ABSTRACT

                       

Purpose:

Osteoporosis is characterized by low bone mineral density (BMD) and high risk of osteoporotic fracture (OF). Peripheral blood monocytes (PBM) can differentiate into osteoclasts to resorb bone. This study was to identify PBM-expressed proteins significant for osteoporosis in Chinese Han elderly population (>65 years), and focused on two phenotypes of osteoporosis: low BMD and OF.

Methods:

Label-free quantitative proteomics was employed to profile PBM proteome and to identify differentially expressed proteins (DEPs) between OF (N=27) vs. non-fractured (NF, N=24) subjects and between low BMD (N=12) vs. high BMD (N=12) subjects in women. Western blotting (WB) was conducted to validate differential expression, and ELISA to evaluate translational value for secretory protein of interest.

Results:

We discovered 59 DEPs with fold change (FC)>1.3 (P<1×10-5), and validated the significant up-regulation of pyruvate kinase isozyme 2 (PKM2) with osteoporosis (P<0.001). PKM2 protein upregulation with OF was replicated with PBM in men (P=0.04). Plasma PKM2 protein level was significantly elevated with OF in an independent sample (N=100, FC=1.68, P=0.01). Pursuant functional assays showed that extracellular PKM2 protein supplement not only promoted monocyte trans-endothelial migration, growth, and osteoclast differentiation (marker gene expression), but also inhibited osteoblast growth, differentiation (ALP gene expression), and activity.

Conclusion:

The above findings suggest that PKM2 protein is a novel osteoporosis-associated functional protein in Chinese Han elderly population. It may serve as a risk biomarker and drug target for osteoporosis.

KEYWORDS:

• BMD
• osteoporosis
• osteoporotic fracture
• PKM2
• proteomics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author Contribution

Fei-Yan Deng and Shu-Feng Lei designed and coordinated the study; Qing Xu, Chun-Hui Li, Long-Fei Wu, and Xu Zhou performed the functional experiments; Chang-Hua Tang and Xiao-Li Huang recruited the samples; Qing Xu and Chun-Hui Li analyzed the data and drafted the manuscript; Fei-Yan Deng revised and finalized the manuscript.

Ethical Approval

The study was approved by the Institutional Research Ethics Board at the Soochow

University and ethics approval number was 201,401. All the participants signed the informed consent form.

Additional information

Funding

The study was supported by the Natural Science Foundation of China 81373010, 82173598, 82173529, and 82373587), the Science and Technology Project of Suzhou (SS202050, SYS2019024), the Project of the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the QingLan Project of Higher Education of Jiangsu Province. The proteome-wide protein expression profiling was conducted/serviced by the Aptbiotech Company (Shanghai, China).