Diseases of Bone and Cartilage

BMD in Osteoporosis Associated With Alterations in Abundance of Gut Microbiota

Emily Pond
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Studies have shown that healthy human gut microbiomes consist of approximately 1150 bacterial species, with most (50%–75%) being Firmicutes species, followed by Bacteroides (10%–50%), Actinobacteria (1%–10%), and Proteobacteria (<1%) species.2 The microbiome in patients with arthritis has been found to be significantly different from that of healthy people, often with increases in nonbeneficial or harmful bacteria, and decreases in beneficial bacteria. Numerous bacterial species have been associated with arthritis, including Bacteroides species, Prevotella species (particularly P copri), and infectious pathogens such as Chlamydia trachomatis, Salmonella, Campylobacter, Yersinia, and Shigella, especially in cases of reactive arthritis.2 Photo credit: SPL / Science Source
Studies have shown that healthy human gut microbiomes consist of approximately 1150 bacterial species, with most (50%–75%) being Firmicutes species, followed by Bacteroides (10%–50%), Actinobacteria (1%–10%), and Proteobacteria (<1%) species.2 The microbiome in patients with arthritis has been found to be significantly different from that of healthy people, often with increases in nonbeneficial or harmful bacteria, and decreases in beneficial bacteria. Numerous bacterial species have been associated with arthritis, including Bacteroides species, Prevotella species (particularly P copri), and infectious pathogens such as Chlamydia trachomatis, Salmonella, Campylobacter, Yersinia, and Shigella, especially in cases of reactive arthritis.2 Photo credit: SPL / Science Source
Researchers determined whether gut microbiota was associated with bone mineral density in individuals at high risk for reduced BMD and fractures.

Gut microbiota alterations were associated with reduced bone mineral density (BMD) in older adults with osteoporosis and osteopenia, per study data results published in Rheumatology.

The study cohort comprised 181 patients with osteoporosis or osteopenia (age range, 55-75 years) recruited from the bone densitometry unit at Cork University Hospital in Ireland. Patients underwent dual energy x-ray absorptiometry assessment of BMD at the femoral neck and anteroposterior lumbar spine. Patients were divided into 3 groups based on BMD: normal (T-score ≥-1; n=60), osteopenia (T-score -1 to -2.5; n=61), and osteoporosis (T-score ≤-2.5; n=60). Patients also provided stool samples, from which genomic DNA was extracted. The V3-V4 region of the 16S rRNA gene was amplified and sequenced to identify differentially abundant taxa. Analyses were adjusted for demographic and clinical data.

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Age and sex composition were comparable across patient groups, although significant differences in body mass index (BMI) and other clinical variables were observed. Compared with the age- and sex-matched control groups, 6 genera in the osteoporosis or osteopenia groups were significantly altered in abundance. BMD was significantly associated with alterations in the microbiota, with both femoral neck and anteroposterior lumbar spine BMD measurements explaining a significant amount of microbiota variance (P ≤.05). A total of 20 metadata variables were found to be associated with the global microbiota profile, including BMI (2.1%), health status, diet, and medication exposure.

A cumulative range of 15% to 17% of microbiota variance was explained by these metadata: with different medications (4.8%), anthropometric measures (3.5%), chronic diseases (3.5%), and BMD measurement (2.0%). After adjustments for sex and BMI, Actinomyces, Eggerthella, Clostridium Cluster XIVa, and Lactobacillus were more abundant in patients with osteoporosis compared with patients in the normal BMD group. Compared with patients in the osteoporosis group, patients in the osteopenia group had greater abundance of Escherichia/Shigella and Veillonella. According to bivariate models adjusted for confounders, just 5 of the 6 identified genera remained significantly differentially abundant across patient groups compared with the control group. Overall microbiota alpha diversity was not correlated with BMD.

These data identify taxa-specific differences in gut microbiota among patients with normal BMD, osteoporosis, and osteopenia, suggesting that specific genera may affect bone metabolism. The identified genera may have utility as biomarkers and therapeutic targets among patients with low BMD.

Reference

Das M, Cronin O, Keohane DM, et al. Gut microbiota alterations associated with reduced bone mineral density in older adults [published online August 4, 2019]. Rheumatology (Oxford). doi:10.1093/rheumatology/kez302

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