Naturally plant-derived compounds: role in bone anabolism.

From a nutritional point of view, several factors are involved in ensuring optimal bone health. The most documented of these are calcium and vitamin D. However, it is now well acknowledged that some phytochemicals, also known as phytonutrients, which are plant-based compounds that are present in our daily diet, can positively regulate a number of physiological functions in mammalian systems involved in chronic diseases such as osteoporosis. Indeed, emerging data in animal models of postmenopausal osteoporosis has shown that exposure to some of these naturally plant-derived compounds (e.g. flavonoids) positively influences bone metabolism through preserved bone mineral density. In vitro experiments with bone cells have reported cellular and molecular mechanisms of phytonutrients involved in bone metabolism. Indeed, phytonutrients and especially polyphenols can act on both osteoblasts and osteoclasts to modulate bone metabolism, a balance between both cell type activities being required for bone health maintenance. To date, most studies investigating the effects of polyphenols on osteoblast cells have reported involvement of complex networks of anabolic signalling pathways such as BMPs or estrogen receptor mediated pathways. This review will report on the interaction between phytochemicals and bone metabolism in cell or animal models with a particular focus on the molecular mechanisms involved in the bone anabolic response.