Effects of the gut microbiota on bone mass

• Studies in germ-free (GF) mice demonstrate that the gut microbiota (GM) is a regulator of bone mass.
• The GM affects bone mass via effects on the immune status, which in turn regulates osteoclastogenesis.
• Probiotic and prebiotic treatments may impact GM composition and affect bone metabolism.
• The GM may be a novel therapeutic target for osteoporosis.

The gut microbiota (GM), the commensal bacteria living in our intestine, performs numerous useful functions, including modulating host metabolism and immune status. Recent studies demonstrate that the GM is also a regulator of bone mass and it is proposed that the effect of the GM on bone mass is mediated via effects on the immune system, which in turn regulates osteoclastogenesis. Under normal conditions, the skeleton is constantly remodeled by bone-forming osteoblasts (OBs) and bone-resorbing osteoclasts (OCLs), and imbalances in this process may lead to osteoporosis. Here we review current knowledge on the possible role for the GM in the regulation of bone metabolism and propose that the GM might be a novel therapeutic target for osteoporosis and fracture prevention.