Treatment with friendly bacteria widely used in probiotic supplements can strengthen bones, a study has found.
Healthy mice fed Lactobacillyus rhamnosus GG (LGG) bugs experienced an immune response that stimulated an increase in bone density.
The effect was linked to the generation of butyrate, or butyric acid – a type of fatty acid produced by gut bacteria.
This in turn activated regulatory T-cells, part of the immune system.
Scientists hope the discovery will lead to new ways of treating the brittle bone disease osteoporosis.
The condition, a major hazard for women after the menopause, can lead to disabling bone fractures and an increased risk of death.
Previous research on animals had suggested that probiotics could help prevent disease-related bone loss, but scientists were unclear why.
Professor Roberto Pacifici, from Emory University in the US, who led the new study, said: “Because their mechanism of action in bone is unknown, they are regarded as some kind of alternative, esoteric, unproven treatment.
“Our goal was to identify a biological mechanism of action of probiotics, a mechanism that makes sense to traditional scientists, hoping that this will make probiotics a mainstream treatment.”
The team discovered that four weeks of LGG supplementation boosted bone formation in female mice by stimulating the growth of butyrate-producing gut bacteria.
LGG had no effect on bone mass when mice were raised in a germ-free environment, showing that it worked in conjunction with other intestinal bugs.
Both LGG and butyrate induced the expansion of regulatory T-cells in the bone marrow.
The T-cells in turn secreted a protein called Wnt10b known to be critical for bone development, the scientists reported in the journal Immunity.
Prof Pacifici said: “We were surprised by the potency of the gut microbiome (bacterial population) in regulating bone and by the complexity of the mechanism of action of probiotics.
“In general, there is a lot of interest in the concept that the gut bacteria regulate the function of distant organs. How this happens is largely unknown.
“We described a detailed mechanism by which changes in the composition of the gut microbiome induced by probiotics affect a distant system like the skeleton.”
Lactobacillus rhamnosus GG is widely sold as an over-the-counter probiotic. It is said to balance the immune system, protect against allergies and irritable bowel syndrome (IBS), and help prevent infections. There are also claims that it has anti-cancer properties.
The team now plans to expand the research and investigate whether butyrate supplementation can combat osteoporosis.
Prof Pacifici added: “Our findings will need to be validated in human studies.
“If successful, this research could substantiate the use of butyrate or probiotics as a novel, safe, and inexpensive treatment for optimising skeletal development in young people and to prevent osteoporosis in older people.”
