The Gut Microbiome and Bone Strength

Abstract

Purpose of review: Osteoporosis is commonly diagnosed through the clinical assessment of bone quantity using bone mineral density; however, the primary clinical concern is bone fragility. Bone fragility is determined by both bone quantity and bone quality. Over the past decade, the gut microbiome has emerged as a factor that can regulate diseases throughout the body. This review discusses how microbial organisms and their genetic products that inhabit the gastrointestinal tract influence bone quantity, bone quality, and bone strength.

Recent findings: Recent studies have shown that the gut microbiome regulates bone loss during estrogen depletion and glucocorticoid treatment. A series of studies has also shown that the gut microbiome influences whole bone strength by modifying bone tissue quality. The possible links between the gut microbiome and bone tissue quality are discussed focusing on the effects of microbiome-derived vitamin K. We provide a brief introduction to the gut microbiome and how modifications to the gut microbiome may lead to changes in bone. The gut microbiome is a promising target for new therapeutic approaches that address bone quality in ways not possible with current interventions.

Keywords: Bone material properties; Bone quality; Bone quantity; Gut microbiome; Vitamin K.

Figure 1.

A cartoon illustrating links between the gut microbiome and bone in some of the studies discussed in this review [, , ••, ••]. Microbial short chain fatty acids, stimulation of the immune system and microbe-derived vitamin K have been proposed/shown to influence osteoclast and osteoblast activity.

Figure 2.

The relationship between probability of hip fracture and whole bone strength determined using participant specific finite element models from computed tomography images is shown for women and men [70]. The solid line indicates the age-adjusted logistic regression model expressing fracture probability v. whole bone strength estimated from finite element models assuming normal bone tissue quality (as reported by [56]). Dashed lines indicate the 95% confidence interval of the logistic regression. An impairment of bone tissue quality that reduces whole bone strength by 20% increases the probability of fracture by 100% (red single-headed arrows). The range of whole bone strength corresponding to individuals with osteoporosis and osteopenia as defined by BMD is indicated [56].