*3.1. E*ff*ect of Curcumin on the Viability of MC3T3 Cells in High-Glucose Conditions*

The proliferation of MC3T3 treated by curcumin under different concentrations of glucose was investigated by using a CCK-8 kit at 24, 48, and 72 h. No differences could be found among each group at 24 h. Cell viability in the control group increased most up to 48 h, and was significantly higher than that in the other groups (*p* < 0.05). The high-glucose group had the lowest cell viability, indicating that a higher concentration of glucose severely affected cell viability. When curcumin was introduced, cell viabilities in different glucose groups significantly increased (*p* < 0.05), whereas there were no differences between low and high concentrations of curcumin treatment. At 72 h, the cell viability in the curcumin-treated groups was significantly higher than that in the glucose groups (*p* < 0.05; Figure 1). Three concentrations of glucose were selected in present study. At 16.5 mmol/L glucose, there was a negative influence on cell viability. No differences were found on the effect of concentrations of curcumin among curcumin-treated groups.

**Figure 1.** Effects of curcumin on viability of MC3T3 cells in high-glucose conditions. Cell viability was measured using the CCK8 assay after culturing for 24, 48, and 72 h, separately. The bar chart shows the mean optical density (OD) values (*n* = 3). \**p* < 0.05 vs the control group; #*p* < 0.05 vs the medium glucose group; *p* < 0.05 vs the high-glucose group.
