Osteoporosis is a systemic skeletal disease that causes bone weakness and fragility. Consuming bone-beneficial nutrients through diet can prevent and treat osteoporosis. Acer palmatum (Japanese maple) leaves are used to make tea, but there have been few reports of their health benefits, especially regarding bone homeostasis. In this study, we evaluated the effects of A. palmatum hot water extract (APE) on osteoclastogenesis and osteoblastogenesis in cultured cells. APE suppressed the number of tartrate-resistant acid phosphatase-positive multinucleated osteoclasts in RANKL induced RAW264.7 cells. Furthermore, APE facilitated Alkaline phosphatase activity and calcium deposition during osteoblast differentiation in MC3T3–E1 cells. High-performance liquid chromatography analysis was performed to investigate the effective components of APE, and four flavonoids orientin, isoorientin, vitexin, and isovitexin were identified with the LC-MS analysis. Treatment with fractionated APE suppressed osteoclastogenesis and facilitated osteoblastogenesis in cultured cells. These findings suggest that APE contains antiosteoporotic compounds; thus, APE might have health promoting effects that help prevent osteoporosis by inhibiting osteoclastogenesis and facilitating osteoblastogenesis.

Mononuclear osteoclast precursor cells fuse with each other to become mature multinucleated osteoclasts, which is regulated by dendritic cell-specific transmembrane protein (DC-STAMP). We evaluated the effects of tea extract and catechins on cell-cell fusion and DC-STAMP expression to elucidate their relationship with osteoclast development. When tea extract or epigallocatechin gallate (EGCg) was applied to RAW264.7 cells, multinucleated cells were increased significantly, while tartrate-resistant acid phosphatase (TRAP) activity was hardly upregulated. Flow cytometric analysis revealed that EGCg suppressed DC-STAMP expression on the cell surface, which is similar to osteoclast development. These observations suggest that TRAP activity is not activated even when suppression of both surface DC-STAMP expression and multinucleation occurs, which might be mediated by another pathway.

Cerebellar granule cell migration plays a crucial role in cerebellum development, and any abnormalities in CGC migration can lead to significant neurological disorders such as anxiety, a common psychological disorder that impacts a person's emotional, physical, and social health. L-theanine, an amino acid found in green tea, demonstrates neuroprotective properties and regulates the release of neurotransmitters by stimulating CGC migration. This study investigated the impact of L-theanine on CGC migration related to cognitive disorders. ddY male mice treated with a single oral dose of L-theanine at varying concentrations (10 mg/kg) were assessed for anxiety, learning, and memory using the maze test and the Morris Water Maze test, where the average completion time and escape time of the mice were considered indicators of cognitive performance. CGC microexplants were isolated from newly born C57BL/N6 mice and treated with a series of increasing concentrations of L-theanine. The migration distance of the CGC under the different L-theanine concentrations was assessed after 24, 48, and 72 h post-treatment using phase-contrast microscopy and image analysis software. Mice's anxiety symptoms improved based on their performance on the maze test after treatment with L-theanine at 5 mg/ml. However, L-theanine at 0.05 mg/ml enhanced learning and memory abilities. Compared to other concentrations, L-theanine at 1 µM yielded the longest migration distance for CGC in vitro. Therefore, L-Theanine may serve as a potential therapeutic agent in supporting cerebellar development and enhancing cognitive skills. Further investigation is required to fully elucidate the molecular mechanisms and therapeutic potential of L-theanine in neurodevelopmental disorders.