Gut microbiota and metabolite alterations associated with reduced bone mineral density or bone metabolic indexes in postmenopausal osteoporosis

Abstract

Reduced bone mineral density (BMD) is associated with an altered microbiota in senile osteoporosis. However, the relationship among gut microbiota, BMD and bone metabolic indexes remains unknown in postmenopausal osteoporosis. In this study, fecal microbiota profiles for 106 postmenopausal individuals with osteopenia (n=33) or osteoporosis (n=42) or with normal BMD (n=31) were determined. An integrated 16S rRNA gene sequencing and LC-MS-based metabolomics approach was applied to explore the association of estrogen-reduced osteoporosis with the gut microbiota and fecal metabolic phenotype. Adjustments were made using several statistical models for potential confounding variables identified from the literature. The results demonstrated decreased bacterial richness and diversity in postmenopausal osteoporosis. Additionally, showed significant differences in abundance levels among phyla and genera in the gut microbial community were found. Moreover, postmenopausal osteopenia-enriched N-acetylmannosamine correlated negatively with BMD, and distinguishing metabolites were closely associated with gut bacterial variation. Both serum procollagen type I N propeptide (P1NP) and C-terminal telopeptide of type I collagen (CTX-1) correlated positively with osteopenia-enriched Allisonella, Klebsiella and Megasphaera. However, we did not find a significant correlation between bacterial diversity and estrogen. These observations will lead to a better understanding of the relationship between bone homeostasis and the microbiota in postmenopausal osteoporosis.

Keywords: 16S rRNA gene sequencing; LC-MS metabolomics; gut microbiota; postmenopausal osteoporosis.

Figure 1

Flow diagram of this study. Osteoporosis: postmenopausal osteoporosis; Osteopenia: postmenopausal osteopenia.

Figure 2

Decreased bacterial richness and diversity in postmenopausal osteoporosis and the alpha metrics were significant associated with LS.BMD. (A) Rarefaction curves for alpha richness in postmenopausal osteopenia, postmenopausal osteoporosis and control. The different facets show the different richness metric cures, the x-axis shows the number of reads, and the y-axis shows the richness metric. The shadow area shows standard deviation of each group. The curves in each group are near smooth when the number of reads is great enough with few OTUs undetected. (B) Comparison of α-diversity (Observe Species and Shannon) based on the OTU profile in each group. The p values are from Mann-Whitney test. (C) Correlation between bacterial diversity and LS.BMD. The x-axis shows the LS.BMD, and the y-axis shows the diversity values. The correlation is calculated with Spearman method.

Figure 3

Discriminative taxa between postmenopausal osteopenia and control. (A) The point plot of LDA (Linear discriminant analysis) shows the features detected as statistically and biologically differential taxa between the different communities. (B) The taxonomic representation of statistically and biologically differences between postmenopausal osteopenia and control. The color of discriminative taxa represents the taxa is more abundant in the corresponding group (Control in green, postmenopausal osteopenia in purple). The size of point shows the negative logarithms (base 10) of p-value. The bigger size of point shows more significant (lower p-value).

Figure 4

Discriminative fecal metabolites between postmenopausal osteopenia and control. (A), As well as between postmenopausal osteoporosis and control (B). The x-axis shows the logarithms (base 10) of LDA (Linear discriminant analysis). The y-axis shows the discriminative fecal metabolites.

Figure 5

The relationship among the discriminative genera, discriminative fecal metabolites and the clinical index associated with osteoporosis. The colors of points show the different phyla of the genera. The size of points of genera shows the mean relative abundance. The circle points represent the clinical indexs, triangle points represent the discriminative genera, and diamond points represent the discriminative fecal metabolites. The transparency of lines represents the negative logarithms (base 10) of p-value of correlation (Spearman), the red lines represent the negative correlation and blue lines represent positive correlation, and the width of lines represents the size of correlation (Spearman).