Enzymatically hydrolyzed steam-exploded rice bran alleviates bone loss in D-galactose-induced aging mice through modulation of the gut-bone axis.

Osteoporosis represents a major challenge to skeletal health during aging, and dietary strategies have gained increasing attention as potential modulators of bone metabolism. This study evaluated the effects of enzymatically hydrolyzed steam-exploded rice bran (ESRB) on bone metabolism in D-galactose-induced aging mice. D-Galactose exposure caused behavioral impairment, deterioration of bone microarchitecture, and gut microbial dysbiosis. ESRB supplementation alleviated behavioral and skeletal alterations in a dose-dependent manner, as evidenced by improved locomotor activity, cognitive performance, and motor coordination, together with increased bone mineral density (BMD) and bone volume fraction (BV/TV), reduced trabecular separation (Tb·Sp), elevated serum bone-specific alkaline phosphatase (BALP), more evident osteocalcin (OCN) positive staining, and increased calcium and phosphorus contents in the distal femur. ESRB also improved intestinal barrier-related and antioxidant indicators, including increased zonula occludens-1 (ZO-1) and claudin-1 mRNA expression, enhanced total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity, and reduced malondialdehyde (MDA) levels, with the most pronounced effects observed in the high-dose group. High-dose ESRB also modulated gut microbiota composition by enriching Muribaculaceae-related taxa (Muribaculum and Paramuribaculum) and reducing Helicobacter rodentium and Heminiphilus faecis, accompanied by increased production of short-chain fatty acids (SCFAs), including acetic acid, propionic acid, butyric acid and valeric acid. Correlation analysis further revealed significant associations among SCFAs, gut microbiota, and bone-related parameters. These findings suggest that ESRB alleviates aging-associated bone loss through modulation of the gut-bone axis.