(P20-040-23) Probiotic Supplementation Improves Fracture-Related Pain in Mice

Objectives: Emerging evidence suggests that the gut microbiota is not only a regulator of bone fracture healing but also contributes to inflammatory pain. Importantly, the gut microbiota can be targeted for therapeutic benefit using nutrition-based approaches such as probiotics. This study sought to determine if daily probiotic supplements would alleviate pain after fracture.

Methods: Female 12-week-old C57BL/6J mice were subjected to experimental mid-diaphyseal unilateral femoral fractures. Six hours post-injury, mice were randomly assigned to receive the probiotic species Bifidobacterium longum (B. longum; 1x10⁸ CFU) or Lactobacillus casei (L. casei; 1x10⁸ CFU) or PBS control via a daily oral gavage. Rearing behavior and gait analysis were used to assess non-stimulus evoked pain. Body composition was assessed using dual-energy absorptiometry. Sera was isolated from fasted mice and used for untargeted metabolomics. All outcomes were assessed prior to fracture and at days 3 and 7 post-fracture.

Results: Probiotic supplementation did not influence whole-body bone mineral density, bone mineral content, fat tissue, or lean tissue post-fracture. B. longum supplementation prevented post-traumatic bone loss within the lumbar spine at day 7. At day 3 post-fracture, B. longum-supplemented mice reared significantly more than controls; whereas, at day 7 post-fracture both B. longum and L. casei supplemented mice reared more than controls. Moreover, the B. longum-supplemented mice displayed improved hindlimb temporal symmetry and a more balanced gait at day 3 post-fracture. Untargeted metabolomics and pathway analysis revealed a significant change in several metabolic pathways in response to fracture, including linoleic acid metabolism and tryptophan metabolism. PLS-DA analyses revealed clear separation between control and probiotic-supplemented mice at day 3 and 7 post-fracture. Correlation analyses identified 108 metabolites that were significantly associated with rearing behavior, an indicator of hindlimb pain.

Conclusions: Probiotic supplementation led to improved pain and functional outcomes during the early post-fracture period in a species-dependent manner. This study highlights the potential utility of targeting the gut microbiota for improved outcomes after fracture.

Funding Sources: Funding provided by the Atlanta VA Health Care System.