Study on the role of FoxO1 in the regulation of osteoblastic metabolism by 1,25(OH)₂D₃ in a high glucose environment

To explore the effect of 1,25(OH)₂D₃ on the regulation of bone metabolism in a high-glucose environment and to provide evidence for the possible regulatory mechanism of 1,25(OH)₂D₃ on osteoblasts in a high-glucose environment.

The osteoblast cell line MC3T3-E1 was cultured in 3 groups: ① control group, cultured in low-glucose (5.5 mmol/L) DMEM; ② high-glucose group: cultured in high-glucose (22 mmol/L) DMEM; ③ high-glucose +1,25(OH)₂D₃ group: high-glucose DMEM + 1,25(OH)₂D₃ medium culture. The CCK-8 method was used to detect cell proliferation in each group; Annexin V and FITC apoptosis kits were used to detect apoptosis; Alizarin red was used to semiquantitatively analyze cell differentiation; qRT-PCR was used to detect forkhead transcription factor-1 (forkhead transcription factor 1, FoxO1) mRNA expression. Immunofluorescence was used to observe the changes in FoxO1 protein expression and its relative position in the nucleus.

Our analysis showed that compared with those in the control group, the osteoblast apoptosis and proliferation in the high-glucose group were improved, while differentiation was inhibited (P < 0.05); at the same time, the mRNA expression of FoxO1(P = 0.006) was reduced. The immunofluorescence results showed that more FoxO1 was inside the nucleus (P < 0.001). Compared with those in the high-glucose group, excessive proliferation was inhibited, apoptosis was reduced, and osteogenic differentiation was improved in the high-glucose +1,25(OH)₂D₃ group (P < 0.05); furthermore, FoxO1 mRNA was decreased (P = 0.006), and the transfer of FoxO1 protein was blocked (P < 0.001).

We found that 1,25(OH)₂D₃ may prevent the transfer of FoxO1 to the cell nucleus, inhibit the abnormal proliferation and apoptosis of osteoblasts in a high-glucose environment, and reverse the inhibitory effect of high glucose on the differentiation of osteoblasts.