Bioactive isoprenylflavonoids contribute to the dual protective effects of Xianling Gubao against sarcopenia and osteoarthritis in SAMP8 mice

Background Osteoarthritis and sarcopenia increasingly contribute to the burden of age-related musculoskeletal disorders. Xianling Gubao (XLGB), a traditional Chinese medicine formula, has been used for musculoskeletal conditions including osteoporosis and osteoarthritis; however, its effects on sarcopenia and structural joint degeneration, and the bioactive compounds potentially associated with dual musculoskeletal protection remain insufficiently defined. This study aimed to evaluate the effects of XLGB on sarcopenia and osteoarthritis, and to identify bioactive compounds associated with its musculoskeletal benefits. Methods Thirty 27-week-old male senescence-accelerated mouse prone 8 (SAMP8) mice were randomly assigned to aging control (SAMP8 with vehicle), low-dose XLGB (80 mg/kg/day), and high-dose XLGB (240 mg/kg/day) groups. Ten age-matched senescence-accelerated mouse resistant 1 (SAMR1) mice served as normal controls. An independent 27-week SAMP8 baseline cohort was included to characterize age-associated changes in muscle contractile and OA-related parameters. Sarcopenia-related changes were assessed by longitudinal body-weight-normalized grip strength, isolated muscle contraction tests, histology, transmission electron microscopy, and real-time quantitative PCR. Osteoarthritis-related changes were evaluated by micro-CT and histology. Exploratory correlation analyses were performed to examine statistical associations between selected sarcopenia- and osteoarthritis-related parameters. HPLC-UV-based chemical fingerprinting was used to characterize XLGB, and representative compounds were selected for CCK-8-based cytotoxicity evaluation and C2C12 myotube formation assays. Results At 37 weeks of age, SAMP8 mice exhibited coexisting sarcopenia- and osteoarthritis-related phenotypes, characterized by reduced muscle mass and contractile function, increased Osteoarthritis Research Society International (OARSI) scores, and impaired subchondral bone microstructure. XLGB produced distinct response patterns across tissues and doses: the lower dose improved selected ex vivo muscle contractile and mitochondrial parameters, whereas the higher dose more consistently attenuated cartilage degeneration; both doses improved selected subchondral bone parameters. Neither dose significantly improved body-weight-normalized forelimb grip strength or altered osteophyte severity. Exploratory correlation analyses showed that muscle contractile force was positively associated with selected subchondral bone parameters, whereas specific tetanic force was negatively associated with OARSI scores. HPLC-UV profiling putatively identified 54 compounds in XLGB, from which 14 representative compounds were selected for in vitro screening. Four compounds, icariin, 2″- O -rhamnosyl icariside II, loganic acid, and sweroside, promoted C2C12 myotube formation. Integration with previously reported anti-osteoarthritic compounds from XLGB identified icariin and 2″- O -rhamnosyl icariside II as candidate shared bioactive constituents potentially associated with the effects of XLGB in muscle and joint tissues. Conclusion XLGB produced distinct beneficial response patterns across tissues and doses in 37-week-old male SAMP8 mice with coexisting sarcopenia- and osteoarthritis-related phenotypes. Icariin and 2″- O -rhamnosyl icariside II were identified as candidate shared bioactive constituents, although their contributions to the in vivo effects of XLGB require further validation. Translational potential of this article : This study supports the utility of 37-week-old male SAMP8 mice for evaluating coexisting sarcopenia- and osteoarthritis-related phenotypes. The findings provide preclinical evidence that XLGB can beneficially influence both skeletal muscle dysfunction and OA-related joint degeneration. The tissue-specific dose responses highlight the need for dose optimization and further evaluation of efficacy, safety, and reproducibility in additional preclinical models before clinical translation.