Gut Bacteria Hinders Bone Growth in the Post-Pubertal Skeleton

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A new study shows that bacteria in the intestinal microbiota can influence the immune system and hinder bone growth after puberty.

Osteoporosis

The bacteria that colonize our intestines can affect our health in many ways from depression and anxiety to arterial health. Gut bacteria can actually regulate our biological functions, including those of the skeleton. Researchers at South Carolina Medical University have studied the influence of certain bacteria, segmented filamentous bacteria (SFB), on the development of the post-pubertal skeleton. Their results, published in the Journal of Bone and Mineral Research Plus, show that these bacteria increase the response of immune cells in the intestine and liver. This disrupts the accumulation of bone mass.

“This is the first known report to show that within the complex gut microbiome, specific microbes have the capacity to affect normal skeletal growth and maturation,” said Chad M. Novince, D.D.S., lead author of the study. He and his team are focusing on the development of the post-pubertal skeleton. During this time, a person’s bone mass increases by 40%. To analyze the effects of segmented filamentous bacteria on skeletal health, the researchers worked on mice with a defined microbiota. One group of mice had segmented filamentous bacteria and the other group was missing them. The composition of the bone is based on the balance between osteoblasts and osteoclasts. Osteoblasts are involved in bone formation and osteoclasts are involved in bone resorption, which is necessary to maintain bone strength. “SFB colonization caused a shift in both sides of the axis: the osteoclast activity went up, and the osteoblast activity went down, which is detrimental to the skeleton.” Professor Novince said.

In addition, the researchers found that the presence of segmented filamentous bacteria stimulates liver immunity. In particular, they increase the immune factors produced in the liver. One of these factors is lipocalin-2, which influences bone metabolism. These results show that the filamentous, segmented bacteria not only have effects on the intestine but also on the liver, which influences bone metabolism.

Modification of the microbiome to maintain bone mass

“If we can avoid colonization or degrade specific microbes, such as segmented filamentous bacteria from the microbiome, there is a clinical potential to optimize the accumulation of bone mass during the development of the postpubertal skeleton,” predicts Chad Novince. The majority of a person’s bone mass accumulates during adolescence and after puberty.

As a person gets older, he or she slowly starts to lose bone mass, with the risk of fractures or osteoporosis. Modulation of the content of segmented filamentous bacteria can reduce the risks of aging. For example, it is already known that diet, probiotics, and antibiotics have important effects on the composition of the microbiota.