Osteogenic Effects of Limosilactobacillus fermentum GBE18 Cell-Free Supernatant (CFS) in MC3T3-E1 Cells via the Wnt/β-Catenin and PI3K/Akt Signaling Pathways

Osteoporosis is a major global health challenge, particularly among aging populations, underscoring the need for safe and effective nutritional interventions. Probiotics and their metabolites have emerged as promising candidates for modulating bone health via the gut-bone axis. In this study, we investigated the effects of a cell-free culture supernatant (CFS) from the food-grade bacterium Limosilactobacillus fermentum GBE18 on the proliferation, differentiation, and mineralization of MC3T3-E1 pre-osteoblasts. GBE18 CFS exhibited no cytotoxicity at concentrations ranging from 1% to 4% (v/v). Notably, 2% (v/v) CFS significantly enhanced alkaline phosphatase (ALP) activity and extracellular matrix mineralization (p < 0.05). Transcriptomic profiling revealed that differentially expressed genes were enriched in osteoblast-related processes and two key signaling pathways: Wnt/β-catenin and PI3K/Akt. Subsequent qRT-PCR and Western blot analyses confirmed the upregulation of critical regulators (Rspo2, Pdpk1, Malat1) and demonstrated coordinated activation of Akt phosphorylation, β-catenin stabilization, and Runx2 protein expression. Our findings indicate that GBE18 CFS promotes osteogenic differentiation through coordinated modulation of the PI3K/Akt and Wnt/β-catenin pathways. Consequently, this study provides mechanistic evidence supporting the potential application of L. fermentum GBE18-derived metabolites as functional food ingredients or dietary interventions for bone health and osteoporosis management.