Stimulation of Wnt/β-Catenin Signaling to Improve Bone Development by Naringin via Interacting with AMPK and Akt.

BACKGROUND/AIMS Naringin is a naturally existing compound in citrus fruits and has been elucidated to promote bone development and maintenance. METHODS The biological roles of naringin were investigated in vitro using osteoblast-like UMR-106 cells, and in vivo through performing ovariectomy to mimic osteoporosis in female mice. Since Wnt/β-catenin signaling is involved in osteoblastogenesis, the effect of naringin on Wnt/β-catenin signaling was studied. RESULTS Naringin promoted the mRNA and protein expressions of β-catenin, and improved Ser552 phosphorylation on β-catenin in UMR-106 cells, which leads to the activation of lymphoid enhancer factor (LEF)/ T-cell factor (TCF) transcription factors. The recruitments of protein kinase B (Akt) inhibitor (Akti-1/2) and AMP-activated protein kinase (AMPK) inhibitor (Dorsomorphin) reduced the influence of naringin on β-catenin phosphorylation, suggesting naringin activates β-catenin via regulating Akt and AMPK. In ovariectomized (OVX) mice naringin treatment improved the bone strength while AMPK and Akt inhibitors partly reversed the effect, which further proved the involvements of Akt and AMPK in the action of naringin in vivo. CONCLUSION Our study points to a novel finding on the mechanism of naringin in facilitating bone formation via Akt and AMPK signaling.