Figure 9. Up-regulation of SIRT1 induced by 17β-E2 promoted autophagy in osteoblasts via AMPK-mTOR pathway. Western blotting showed the expression of p-AMPK, t-AMPK, p-mTOR and β-actin in osteoblasts among the groups. (A) The expression level of AMPK phosphorylation in osteoblasts treated with 17β-E2 (0, 10-8, 10-7, 10-6 M) for 24 h. Cells were pretreated with or without SRT1720 and EX527 for 2 h, and then cultured with 17β-E2 (10-6 M) for 24 h. Western blotting showed the expression of p-AMPK (B), and p-mTOR (C) proteins in osteoblasts. The histograms showed the relative expression of p-AMPK and p-mTOR normalized to β-actin, and the densitometry analysis of the blots were estimated by using the Image J Software. The expression ofSIRT1 (D) mRNA in osteoblasts were measured by RT-PCR. The data were expressed as the means ± SD from 3 independent experiments. Statistically significance was evaluated using the Student’s t-test. * P < 0.05 vs. the control group was considered significant.