Alterations to the gut microbiome impair bone tissue strength in aged mice

Whole bone strength and resistance to fracture are determined by a combination of bone quantity and bone quality - key factors in determining risk for osteoporosis and age-related fractures. Recent preclinical studies have shown that alterations to the gut microbiome can influence bone quantity as well as bone tissue quality. Prior work on the gut microbiome and bone has been limited to young animals, and it is unknown if the gut microbiome can alter bone tissue strength in aged animals. Here we ask if alterations to the constituents of the gut microbiome influence bone strength in older mice (12-24 months of age). Male C57BL/6J mice raised on a standard chow diet until 12 months of age were assigned to one of three diets: high glycemic, low glycemic, or low glycemic diet containing antibiotics (ampicillin and neomycin) to modify the constituents of the gut microbiome. The group fed the low glycemic diet containing antibiotics showed reductions in whole bone strength that could not be explained by geometry, indicating reduced bone tissue strength (p < 0.007). The high glycemic diet group had larger bone cross-sectional area and moment of inertia and a corresponding greater bone strength as compared to the low glycemic groups, however tissue strength did not noticeably differ from that of the low glycemic group. These findings demonstrate that modifying the gut microbiome in aged mice can alter bone tissue quality.