Gut microbiota, inflammatory proteins and bone mineral density in different age groups: A Mendelian randomization study

Several studies have indicated a potential association between gut microbiota and bone density. However, the causal relationship between gut microbiota and bone mineral density across different age groups, as well as the potential role of inflammatory proteins as mediators, remains unclear. Gut microbiota, inflammatory proteins, and bone mineral density (BMD) were identified in various age groups using summary data from large-scale genome-wide association studies. Mendelian randomization was employed to examine the causal connections between gut microbiota, inflammatory proteins, and BMD in different age groups, primarily utilizing inverse variance weighted as the statistical method. Furthermore, the potential role of inflammatory proteins as mediators in the pathway from gut microbiota to BMD was investigated. Eight positive and 19 negative causal relationships between gut microbiota and BMD were observed across various age groups. We also identified 14 positive and 8 negative causal relationships between inflammatory proteins and BMD in different age groups. Inflammatory proteins did not appear to function as mediators in the pathway from gut microbiota to BMD. Gut microbiota and inflammatory proteins were causally linked to BMD; however, inflammatory proteins did not seem to function as mediators in the pathway from gut microbiota to BMD because the effects of intestinal flora on bone density and the effects of inflammatory factors on bone density were in different directions.