Osteoporosis, characterized by excessive osteoclast activity and disrupted bone remodeling, remains a significant health concern. This study investigated the potential of shiitake mushroom (Lentinula edodes) extracts, prepared with various drying methods, to inhibit osteoclast differentiation and promote bone formation. Mushroom stipe extracts, irrespective of the drying method, effectively suppressed osteoclast differentiation by downregulating nuclear factor of activated T-cells, cytoplasmic 1 expression in osteoclast precursor cells treated with macrophage colony-stimulating factor and receptor activator of nuclear factor kappa-Β ligand (RANKL), whereas the mushroom cap extracts exhibited minimal inhibitory effects. This disparity highlights the importance of part-specific analyses as the stipes contained higher levels of bioactive molecules, including denatonium, which was identified as a key RANKL signaling disrupter. In contrast, the caps lacked the anti-osteoclastogenic activity observed in the stipes, which were notably consistent across the freeze-drying, air-drying, and hot-air drying methods, indicating the stability of the bioactive compounds under various processing conditions. In vivo studies using an osteoporosis-induced zebrafish model further validated the therapeutic potential of the stipe extracts, which restored bone mineralization and mitigated prednisolone-induced bone loss. These findings emphasize the importance of identifying and optimizing specific mushroom parts for their unique therapeutic properties. Shiitake mushroom stipe extracts are a natural product potentially useful in osteoporosis therapy. This therapy would be a promising alternative to conventional treatments, such as bisphosphonates, which are associated with adverse side effects.

Ras activates a series of downstream effectors, including the mitogen-activated protein kinase pathway and the Rac/Rho pathway after insulin stimulation. Mutations in Ras are found in approximately 30% of all human cancers and are critical factors in tumor initiation and maintenance. There are four Ras proteins with 80-90% amino acid sequence homology with major differences in the carboxyl termini. Ras proteins undergo farnesylation on their carboxyl termini catalyzed by the enzyme protein farnesyltransferase (FTase), which facilitates localization of Ras proteins to the inner surface of the plasma membrane. Because inhibition of FTase would prevent Ras from processing into its active form, FTase is viewed as a potential therapeutic target. A variety of FTase inhibitors have showed great potency against tumor cells in preclinical studies. Although many farnesyltransferase inhibitors have been developed, their adverse effects on the mitogenic and metabolic actions of insulin are not completely understood. Here we show that YH3096, a farnesyltransferase inhibitor, inhibits insulin-mediated DNA synthesis in HIRc-B cells without affecting c-Jun expression and membrane ruffling in HIRc-B cells. Moreover, YH3096 and its derivatives did not affect insulin-induced glucose uptake in 3T3-L1 adipocytes. Our results provide a laboratory evaluation of the effects of Ras inhibitors on insulin functions.