Effects of probiotic modulation on bone health in estrogen-deficient female Sprague-Dawley rats

Postmenopausal osteoporosis is a common metabolic disorder caused mainly by estrogen deficiency, which accelerates bone resorption, suppresses bone formation, and increases fracture risk in aging women. Emerging evidence suggests that the gut microbiota influences skeletal homeostasis through the gut-bone axis, indicating that probiotic supplementation may provide a novel nutritional strategy for bone protection. This study evaluated the osteoprotective effects of two probiotic strains, Bifidobacterium breve i1088 and Bifidobacterium longum subsp. longum i772, in an ovariectomized Sprague-Dawley rat model of estrogen-deficiency-induced osteoporosis. Female rats were randomly allocated to sham-operated control, ovariectomized model, probiotic treatment, and positive control groups. After intervention, bone mineral density, femoral calcium content, and trabecular microarchitecture were assessed. Compared with untreated ovariectomized rats, probiotic supplementation significantly increased bone mineral density and bone calcium content, improved trabecular thickness, and reduced trabecular separation (P < 0.01). These findings demonstrated that probiotic administration attenuated bone loss and preserved skeletal microstructure under estrogen-deficient conditions. The results provide preclinical evidence that Bifidobacterium-based probiotic formulations may serve as a promising adjunctive nutritional approach for maintaining bone health in postmenopausal women. Further clinical studies are required to confirm their preventive and therapeutic potential in postmenopausal osteoporosis.