Bile salt hydrolase-active bifidobacterium animalis improves sarcopenia via the gut microbiota-bile acid-FXR-FGF15 axis and its functional fermented milk preparation.

Sarcopenia is a major global health challenge associated with aging, and effective pharmacological treatments are lacking. This study investigated how bile salt hydrolase (BSH)-active probiotics alleviate sarcopenia through bile acid deconjugation and remodeling, activating the intestinal FXR-FGF15/19 signaling pathway, and explored their application in functional dairy products. Three high-BSH strains-Lactiplantibacillus plantarum H-87, Bifidobacterium animalis F1-7, and F1-3-2-were identified, among which F1-7 and F1-3-2 showed superior efficacy in a dexamethasone-induced sarcopenia model. These strains improved muscle mass, morphology (including increased muscle fiber cross-sectional area and improved histological integrity), and performance by modulating gut microbiota, optimizing bile acid composition, and enhancing ileal FXR-FGF15 signaling to activate the muscle FGFR4/KLB pathway and inhibit protein degradation. Furthermore, fermented milk produced with F1-7 and F1-3-2 met quality standards and exhibited improved sensory properties. This study provides a mechanistic basis for developing probiotic dairy products and sustainable nutritional strategies for sarcopenia.