Parathyroid hormone–dependent bone formation requires butyrate production by intestinal microbiota
Jau-Yi Li, Mingcan Yu, Subhashis Pal, Abdul Malik Tyagi, Hamid Dar, Jonathan Adams, M. Neale Weitzmann, Rheinallt M. Jones, Roberto Pacifici
Jau-Yi Li, Mingcan Yu, Subhashis Pal, Abdul Malik Tyagi, Hamid Dar, Jonathan Adams, M. Neale Weitzmann, Rheinallt M. Jones, Roberto Pacifici
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Research Article Bone biology

Parathyroid hormone–dependent bone formation requires butyrate production by intestinal microbiota

Abstract

Parathyroid hormone (PTH) is a critical regulator of skeletal development that promotes both bone formation and bone resorption. Using microbiota depletion by wide-spectrum antibiotics and germ-free (GF) female mice, we showed that the microbiota was required for PTH to stimulate bone formation and increase bone mass. Microbiota depletion lowered butyrate levels, a metabolite responsible for gut-bone communication, while reestablishment of physiologic levels of butyrate restored PTH-induced anabolism. The permissive activity of butyrate was mediated by GPR43 signaling in dendritic cells and by GPR43-independent signaling in T cells. Butyrate was required for PTH to increase the number of bone marrow (BM) regulatory T cells (Tregs). Tregs stimulated production of the osteogenic Wnt ligand Wnt10b by BM CD8+ T cells, which activated Wnt-dependent bone formation. Together, these data highlight the role that butyrate produced by gut luminal microbiota plays in triggering regulatory pathways, which are critical for the anabolic action of PTH in bone.

Authors

Jau-Yi Li, Mingcan Yu, Subhashis Pal, Abdul Malik Tyagi, Hamid Dar, Jonathan Adams, M. Neale Weitzmann, Rheinallt M. Jones, Roberto Pacifici

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Figure 7

GPR43 signaling in DCs is required for iPTH treatment to improve trabecular structure, stimulate bone turnover, expand Tregs, and induce Wnt10b expression.

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GPR43 signaling in DCs is required for iPTH treatment to improve trabecu...
TCR-β–/– mice reconstituted with sorted splenic T cells from GPR43–/– or GPR43+/+ littermates were treated with either vehicle or iPTH for 4 weeks. Mice were sacrificed and analyzed at 12 weeks of age. (A and B) μCT scanning measurements of trabecular bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) (n = 10 mice/group). (C and D) Serum levels of osteocalcin and CTX (n = 10 mice/group). (E and F) PP and BM Tregs (CD4+Foxp3+ cells) (n = 10 mice/group). (G and H) Wnt10b mRNA levels in whole BM cells and sorted BM CD8+ T cells (n = 5 mice/group). (I) Number of Tregs in cultures of naive CD4+ T cells from WT or GPR43–/– in the presence of butyrate (n = 5 /group). (J) Number of Tregs in cocultures of WT naive CD4+ T cells, and WT or GPR43–/– DCs pretreated with butyrate (n = 5/group). (K) Number of Tregs in cocultures in naive CD4+ T cells and DCs. WT and GPR43–/– mice were treated with antibiotics for 4 weeks and iPTH or butyrate during the last 2 weeks (n = 10/group, from 2 separate experiments). In I, the cultures were stimulated by anti-CD3 and anti-CD28 antibodies, IL-2, and TGF-β. In J–K, the cultures were stimulated by anti-CD3 antibody and TGF-β. Data were expressed as mean ± SEM. All data were normally distributed according to the Shapiro-Wilk normality test. Data in A–J were analyzed by 2-way ANOVA and post hoc tests, applying the Bonferroni’s correction for multiple comparisons. Data in K were analyzed by 1-way ANOVA and post hoc tests, applying Bonferroni’s correction for multiple comparisons *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 compared with the indicated group in the post hoc tests.