Non-coenzyme role of vitamin B1 in RANKL-induced osteoclastogenesis and ovariectomy induced osteoporosis

Vitamins B are co-enzymes participating in energy metabolic pathways. While some vitamins B are known affecting bone homeostasis, the effects of vitamin B1 (thiamine) on bone health remains unclear. In our study, we used cell counting kit-8, tartrate-resistant acid phosphatase stain, actin cytoskeleton stain, and pit formation assay to evaluate the effect of thiamine on osteoclast differentiation, formation, and function, respectively. Then we used dichloro-dihydro-fluorescein diacetate assay to investigate reactive oxygen species (ROS) generation and removal. Osteoporosis model by ovariectomy was established for animal experiments. We found that thiamine had inhibitory effect on osteoclast differentiation. And its inhibitory role on osteoclast differentiation is in a dose-dependent way. Mechanistically, ThDP suppresses intracellular ROS accumulation and unfolded protein response signaling during osteoclastogenesis via inhibiting Rac-Nox1/2/4 and intracellular inositol-requiring protein-1α/X-box-binding protein pathways, respectively. Osteoporotic mice treated with thiamine rich dietary showed better bone strength relative to thiamine deficient dietary. Our study explored the non-coenzyme inhibitory functions of B1 vitamin in receptor activator of nuclear factor κB ligand induced osteoclastogenesis and uncovered the significance of B1 vitamin in bone health.