Effect of pinocembrin isolated from Alpinia zerumbet on osteoblast differentiation

Bone mass is regulated by osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Osteoporosis is a bone metabolism disorder in which bone mass decreases due to increased bone resorption rather than bone formation. We focused on the traditional plantAlpinia zerumbetin Okinawa, Japan, and searched for promising compounds for the prevention and treatment of osteoporosis. Pinocembrin isolated from the leaves ofA. zerumbetshowed enhanced alkaline phosphatase (ALP) activity and mineralization and increased mRNA expression of osteoblast-related genesAlpandOsteocalcin(Ocn) in MC3T3-E1 cells. Pinocembrin increased the mRNA expression ofRunx2andOsterix, which are important transcription factors in osteoblast differentiation, and the mRNA expression ofDlx5andMsx2, which are enhancers of these transcription factors. The bone morphogenetic protein (BMP) antagonist noggin, its receptor kinase inhibitor LDN-193189 and p38 MAPK inhibitor SB203580 attenuated pinocembrin-promoted ALP activity. Pinocembrin increased the mRNA ofBmp-2and its target geneId1. In addition, the estrogen receptor (ER) inhibitor ICI182780 suppressed pinocembrin-stimulated ALP activity. Pinocembrin may increase BMP-2 expression via ER. Then, the BMP-2 promotes osteoblast specific genes expression and mineralization through both Smad-dependent and independent pathway following Runx2 and Osterix induction. Our findings suggest that pinocembrin has bone anabolic effects and may be useful for the prevention and treatment of bone metabolic diseases such as osteoporosis.