抄録
Aim: Bone remodeling by which mature bone tissue is removed by osteoclast and new bone tissue is formed by osteoblast, is important to maintain bone mass and quality. Imbalanced bone homeostasis increases fracture risks and lead to osteoporosis. Accumulation of advanced glycation end products (AGEs) plays a role in diabetic complications and patients with diabetes mellitus have a higher incidence rate of osteoporosis than healthy subjects. In this research, we investigated the effect of AGEs on osteoblast differentiation (osteoblastgenesis).
Methods: For osteoblstgenesis, mouse myoblast C2C12 cells were stimulated with bone morphogenetic protein 2 (BMP2). To determine the effect of AGEs on osteoblastgenesis, cells were treated with BMP2 with or without AGEs, which were formed by glyceraldehyde and human serum albumin (HSA-glycer), and we performed quantitative real-time PCR analysis against alkarine phosphatase (ALP) and osteocalcin (OC), marker of osteoblastgenesis. We further investigated the effect of AGEs on the expression of runt related transcription factor 2 (Runx2) and osterix, major transcription factors of osteoblastgenesis. To see the effect of AGEs on Smad pathway, which partially regulates the BMP2 signaling pathway, western blot analyses against phosphorylation of Smad 1/5/9 were examined. Finally, to evaluate the effect of AGEs on bone turnover, we investigated the ratio of osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL), a major indicator of bone turnover.
Results: HSA-glycer inhibited BMP2-induced expression of ALP and OC. The expression of transcription factors and phosphorylation of Smad 1/5/9 were partially suppressed by HSA-glycer. DeIncreasing OPG/RANKL/OPG ratios by HSA-glycer suggests that AGEs are likely to delay bone turnover.
Conclusion: Our findings indicate that AGEs may inhibit BMP2-induced osteoblastgenesis via alteration of the Smad pathway.
