Cycloastragenol prevents age-related bone loss: Evidence in d-galactose-treated and aged rats

Aging-induced bone loss is a multifactorial, age-related, and progressive phenomenon among the general population and may further progress to osteoporosis and increase the risk of fractures. Cycloastragenol (CAG), currently the only compound reported that activates human telomerase, is thought to be able to alleviate or delay the symptoms of aging and chronic diseases. Previous research has suggested that CAG may have the potential to alleviate age-related bone loss. However, to date, no research has specifically focused on this aspect. In this study, we aimed to investigate whether CAG could prevent senile osteoporosis, and further reveal its underlying mechanism. CAG treatment was administrated into two bone loss rat models (D-galactose administration and aging) for 20 weeks and 33 weeks, respectively. Serum biomarkers analyses, bone biomechanical tests, micro-computed tomography assessment, and bone histomorphometry analyses were performed on the bone samples collected at the endpoint, to determine whether CAG could prevent or alleviate age-related bone loss. Proteomic analysis was performed to reveal the changes in protein profiles of the bones, and western blot was used to further verify the identity of the key proteins. The viability, osteoblastic differentiation, and mineralization of MC3T3-E1 cells were also evaluated after CAG treatment in vitro. The results suggest that CAG treatment improves bone formation, reduces osteoclast number, alleviates the degradation of bone microstructure, and enhances bone biomechanical properties in both d-galactose- and aging-induced bone loss models. CAG treatment promotes viability, osteoblastic differentiation, and mineralization in MC3T3-E1 cells. Proteomic and western blot analyses revealed that CAG treatment increases osteoactivin (OA) expression to alleviate bone loss. The results revealed that CAG alleviates age-related bone loss and improves bone microstructure and biomechanical properties. This may due to CAG-induced increase in OA expression. In addition, the results support preclinical investigations of CAG as a potential therapeutic medicine for the treatment of senile osteoporosis.