Plain language summary
Osteoporosis is a highly prevalent bone disease in the elderly population and is characterised by decreased bone mineral density, deteriorated bone microarchitecture, reduced bone strength and increased susceptibility to fragility fractures. Due to the lack of awareness about osteoporosis, there is the need to develop a novel and effective intervention for its prevention and treatment. The aim of this study was to gain mechanistic insight into the effect of Lactobacillus reuteri ATCC PTA 6475 on bone metabolism and identify factors important for a good response to the probiotic. This study was based on a placebo-controlled cohort trial where 68 elderly women had been randomised to supplementation with the probiotic strain L. reuteri ATCC PTA 6475 or placebo. For this secondary analysis, 20 out of the 68 elderly women with bone loss who supplemented with probiotic L. reuteri ATCC PTA 6475 were selected. Results showed that after one-year probiotic supplementation, there was decreased inflammation and significantly increased gene richness of the gut microbiota in the good responders, whereas there was altered microbial composition and function, including enrichment of E. coli and its biofilm formation in the poor responders. Authors conclude that L. reuteri ATCC PTA 6475 supplementation might promote bone formation by modulating the gut microbiota composition and function, which could be crucial for the development of novel osteoporosis treatments.
Recent studies have shown that probiotic supplementation has beneficial effects on bone metabolism. In a randomized controlled trial (RCT) we demonstrated that supplementation of Lactobacillus reuteri ATCC PTA 6475 reduced bone loss in older women with low bone mineral density. To investigate the mechanisms underlying the effect of L. reuteri ATCC PTA 6475 on bone metabolism, 20 women with the highest changes (good responders) and the lowest changes (poor responders) in tibia total volumetric BMD after one-year supplementation were selected from our previous RCT. In the current study we characterized the gut microbiome composition and function as well as serum metabolome in good responders and poor responders to the probiotic treatment as a secondary analysis. Although there were no significant differences in the microbial composition at high taxonomic levels, gene richness of the gut microbiota was significantly higher (P < 0.01 by the Wilcoxon rank-sum test) and inflammatory state was improved (P < 0.05 by the Wilcoxon signed-rank test) in the good responders at the end of the 12-month daily supplementation. Moreover, detrimental changes including the enrichment of E. coli (adjusted P < 0.05 by DESeq2) and its biofilm formation (P < 0.05 by GSA) observed in the poor responders were alleviated in the good responders by the treatment. Our results indicate that L. reuteri ATCC PTA 6475 supplementation has the potential to prevent a deterioration of the gut microbiota and inflammatory status in elderly women with low bone mineral density, which might have beneficial effects on bone metabolism.