Role of Gut Microbiota in the Skeletal Response to PTH

Exposed surfaces of mammals are colonized with 100 trillion indigenous bacteria, fungi, and viruses, creating a diverse ecosystem known as the human microbiome. The gut microbiome is the richest microbiome and is now known to regulate postnatal skeletal development and the activity of the major endocrine regulators of bone. Parathyroid hormone (PTH) is one of the bone-regulating hormone that requires elements of the gut microbiome to exert both its bone catabolic and its bone anabolic effects. How the gut microbiome regulates the skeletal response to PTH is object of intense research. Involved mechanisms include absorption and diffusion of bacterial metabolites, such as short-chain fatty acids, and trafficking of immune cells from the gut to the bone marrow. This review will focus on how the gut microbiome communicates and regulates bone marrow cells in order to modulate the skeletal effects of PTH.