Metabolomics profiling provides valuable insights into the underlying mechanisms of Morinda officinalis on protecting glucocorticoid-induced osteoporosis.

Morinda officinalis (MO) has long been used as a traditional herbal medicine for the treatment of bone fractures and joint diseases in China. Monotropein (Mon) and rubiadin-1-methyl ether (Rub) are major bioactive components in MO. Ample evidence shows that MO and its chemical constituents can prevent osteoporosis induced by estrogen-deficiency and ageing. However, there is no study reporting glucocorticoid-induced osteoporosis (GIOP). The aim of the present study was to explore the protective effect of MO on GIOP modeled rats and osteoblasts, and elucidate the underlying mechanisms via UHPLC-Q-TOF/MS based metabolomics profiling. Eight weeks after dexamethasone (DEX) injection and MO treatment in female SD rats aged 12 weeks, bone mineral density (BMD), the micro-architecture of the trabecular bone, serum level of bone metabolism markers, and urine metabolomics were assayed in vivo. Cultured osteoblasts were injured with DEX, and the effects of MO, Mon and Rub on osteoblastic proliferation, differentiation and mineralization were examined in vitro. The results showed that MO was able to increase BMD, improve the micro-architecture and intervene bone metabolism via regulating alkaline phosphatase (ALP), tartrate resistant acid phosphatase (TRAP) and c-terminal telopeptides of type I collagen (CTX-I) levels in DEX-treated rats. The in vitro experiment showed that MO, Mon and Rub all increased the cell proliferation and ALP activity, and enhanced extracellular matrix mineralization in DEX-injured osteoblasts. Metabolomics profiling identified a total of 37 differential metabolites in DEX group vs. the control group, of which 20 were reversed significantly after MO treatment. Further metabolic pathway enrichment and Western blotting analysis showed that MO prevented bone loss mainly by interfering with arachidonic acid metabolism. These results suggested MO had a notable anti-GIOP effect, and the underlying mechanisms might be related to arachidonic acid metabolism.