Prospective efficacy of a novel dual-pronged strategy combining the probiotic Lactobacillus casei and Microalga Chlorella vulgaris in preventing postmenopausal bone loss in ovariectomized rats.

Estrogen deficiency drives postmenopausal osteoporosis and increases fracture risk via accelerated bone resorption. This study evaluated the protective efficacy of a dual intervention combining the probiotic Lactobacillus casei (LC) and the microalga Chlorella vulgaris (CV) in a well-established ovariectomized (OVX) rat model of postmenopausal bone loss. Adult female Sprague-Dawley rats (n = 40) underwent sham operation or bilateral ovariectomy. Three months' post-surgery, OVX rats received daily oral gavage of vehicle, LC (1 × 10⁹ CFU/rat), CV (150 mg/kg), or their combination (Combo) for 4 weeks (n = 8 per group). OVX induced hypocalcemia, elevated serum alkaline phosphatase (ALP), and significant reductions in bone mineral density (BMD) and bone mineral content (BMC) assessed by dual-energy X-ray absorptiometry (DEXA) across global, spine, femur, and tibia sites (p < 0.05 vs. sham). While monotherapies provided partial protection, the LC + CV combination demonstrated significantly greater restoration of serum calcium and normalization of ALP levels compared with OVX and monotherapy groups. The combination also produced the most pronounced increases in BMD and BMC at all skeletal sites (p < 0.05 vs. OVX and monotherapies). These findings suggest that LC and CV exert complementary effects, resulting in greater protection against estrogen deficiency-induced bone loss than either treatment alone. In conclusion, this preliminary preclinical study indicates that the LC-CV combination represents a promising multi-targeted natural strategy for postmenopausal osteoporosis that warrants further mechanistic and clinical investigation.