A Standard Herbal Formula, CGAC, Attenuates Bone Loss by Normalizing Low-Bone Turnover Stagnation in an Orchiectomy-Induced Mouse Model

Background/Objectives: Osteoporosis is a progressive systemic skeletal disease, with male osteoporosis emerging as a critical global concern due to high morbidity and mortality from fractures. This study investigated the anti-osteoporotic potential of CGAC—a herbal mixture of Cervus elaphus Linnaeus, Glycine max (L.) Merr., Angelica gigas Nakai, and Cnidium officinale Makino—and its underlying mechanisms in an orchiectomized (ORX) mouse model. Methods: C57BL/6J mice underwent ORX for 8 weeks, followed by CGAC administration (250 and 500 mg/kg) for an additional 8 weeks. Molecular mechanisms were further validated using MG63 osteoblastic and RAW 264.7 osteoclast assays. Results: ORX induced severe osteoporotic phenotypes, including significant reductions in bone mineral density (BMD) and trabecular microarchitecture. Notably, at the time point examined, ORX was associated with a suppressed bone remodeling state, reflected by reductions in both TRAP-positive osteoclasts and ALP-positive osteoblasts, together with lower serum BALP, CTX-1, and Gla/Glu-OC ratio. Conversely, CGAC normalized this stagnant state and restored physiological remodeling. This was accompanied by reduced marrow fat accumulation through the AMPK signaling axis, which upregulated Runx2 and downregulated PPAR-γ. In vitro results confirmed that CGAC promoted osteoblast differentiation and mineralization while suppressing RANKL-induced osteoclastogenesis. These actions suggest that CGAC may be involved in regulating Wnt/β-catenin signaling. Conclusions: Overall, CGAC is a promising therapeutic candidate for male osteoporosis, offering pharmacological benefits particularly relevant to aging populations.