Association Between Gut Microbiota and Bone Health: Potential Mechanisms and Prospective

Genetically predicted elevated circulating 3,4-dihydroxybutyrate levels mediate the association between family Christensenellaceae and osteoporosis risk: a Mendelian randomization study

Objective

To investigate the impact of gut microbiota on osteoporosis and identify the mediating role of blood metabolites in this process.

Methods

This two-sample Mendelian randomization (MR) study utilized summary level data from genome-wide association studies (GWAS). Gut microbiota GWAS data were obtained from the MiBio-Gen consortium meta-analysis (n=13,266), while osteoporosis summary statistics were sourced from the FinnGen consortium R9 release data (7300 cases and 358,014 controls). Metabolite data, including 1400 metabolites or metabolite ratios, were derived from a study involving 8,299 unrelated individuals. The primary MR method employed was the inverse variance weighted (IVW) method. Reverse MR analysis was conducted on bacteria causally associated with osteoporosis in forward MR. The gut microbiota with the smallest p-value was selected as the top influencing factor for subsequent mediation analysis. A two-step MR approach quantified the proportion of the blood metabolite effect on gut microbiota influencing osteoporosis. IVW and Egger methods were used to assess heterogeneity and horizontal pleiotropy.

Results

IVW estimates indicated a suggestive effect of family Christensenellaceae on osteoporosis (odds ratio(OR) = 1.292, 95% confidence interval(CI): 1.110-1.503, P =9.198 × 10-4). Reverse MR analysis revealed no significant causal effect of osteoporosis on family Christensenellaceae (OR = 0.947, 95% CI: 0.836-1.072, P =0.386). The proportion of the effect of family Christensenellaceae on osteoporosis mediated by circulating levels of 3,4-dihydroxybutyrate was 9.727%. No significant heterogeneity or horizontal pleiotropy was detected in the instrumental variables used for MR analysis.

Conclusion

This study establishes a causal link between family Christensenellaceae and osteoporosis, with a minor proportion of the effect mediated by elevated circulating levels of 3,4-dihydroxybutyrate. Further randomized controlled trials (RCTs) are warranted to validate this conclusion.

Gut microbiota, plasma metabolites, and osteoporosis: unraveling links via Mendelian randomization

Objective

Osteoporosis, characterized by reduced bone density and heightened fracture risk, is influenced by genetic and environmental factors. This study investigates the interplay between gut microbiota, plasma metabolomics, and osteoporosis, identifying potential causal relationships mediated by plasma metabolites.

Methods

Utilizing aggregated genome-wide association studies (GWAS) data, a comprehensive two-sample Mendelian Randomization (MR) analysis was performed involving 196 gut microbiota taxa, 1,400 plasma metabolites, and osteoporosis indicators. Causal relationships between gut microbiota, plasma metabolites, and osteoporosis were explored.

Results

The MR analyses revealed ten gut microbiota taxa associated with osteoporosis, with five taxa positively linked to increased risk and five negatively associated. Additionally, 96 plasma metabolites exhibited potential causal relationships with osteoporosis, with 49 showing positive associations and 47 displaying negative associations. Mediation analyses identified six causal pathways connecting gut microbiota to osteoporosis through ten mediating relationships involving seven distinct plasma metabolites, two of which demonstrated suppression effects.

Conclusion

This study provides suggestive evidence of genetic correlations and causal links between gut microbiota, plasma metabolites, and osteoporosis. The findings underscore the complex, multifactorial nature of osteoporosis and suggest the potential of gut microbiota and plasma metabolite profiles as biomarkers or therapeutic targets in the management of osteoporosis.

Adding Vertebral Bone Quality to the Fusion Risk Score: Does It Improve Predictions of Postoperative Complications?

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

The current study evaluates whether the addition of the Vertebral Bone Quality (VBQ) score to the Fusion Risk Score (FRS) improves its ability to predict perioperative outcomes.

SUMMARY OF BACKGROUND DATA

The FRS was developed to assess preoperative risk in patients undergoing thoracic and lumbar fusions. It includes patient-derived and surgical variables, but it does not include one that directly accounts for bone health. The VBQ score allows assessment of bone quality and has been shown to correlate to DEXA-measured bone mineral density (BMD) scores.

METHODS

The VBQ score was weighted based on a regression model and then added to the FRS (FRS/VBQ). The ability of the two scores to predict the outcomes was then assessed using the area under the curve (AUC).

PATIENT SAMPLE

Patients undergoing elective thoracic and lumbar spinal fusion from January 2019 to June 2020 were included.

OUTCOME MEASURES

The study evaluated various perioperative adverse outcomes, including major and minor adverse events, discharge other than home, extended length of stay, 90-day emergency department visits, 90-day readmission, and 90-day and 2-year reoperation rates.

RESULTS

A total of 353 met the inclusion and exclusion criteria. The FRS/VBQ demonstrated improved predictive ability compared with the FRS alone when evaluating 90-day reoperation. Both scores showed fair predictive ability for any adverse event, major adverse events, minor adverse events, and 2-year reoperation rates, with AUCs ranging from 0.700 to 0.737. Both had poor predictive ability for the other outcomes.

CONCLUSIONS

Adding VBQ to the FRS significantly enhances its predictive accuracy for reoperation rate. This updated risk score provides a more comprehensive understanding of a patient's preoperative risk profile, aiding both patients and physicians in assessing surgical risks and optimizing outcomes through preoperative risk stratification.

LEVEL OF EVIDENCE

3.

Hydrolyzed egg yolk peptide prevented osteoporosis by regulating Wnt/β-catenin signaling pathway in ovariectomized rats

Hydrolyzed egg yolk peptide (YPEP) was shown to increase bone mineral density in ovariectomized rats. However, the underlying mechanism of YPEP on osteoporosis has not been explored. Recent studies have shown that Wnt/β-catenin signaling pathway and gut microbiota may be involved in the regulation of bone metabolism and the progression of osteoporosis. The present study aimed to explore the preventive effect of the YPEP supplementation on osteoporosis in ovariectomized (OVX) rats and to verify whether YPEP can improve osteoporosis by regulating Wnt/β-catenin signaling pathway and gut microbiota. The experiment included five groups: sham surgery group (SHAM), ovariectomy group (OVX), 17-β estradiol group (E2: 25 µg /kg/d 17β-estradiol), OVX with low-dose YPEP group (LYPEP: 10 mg /kg/d YPEP) and OVX with high-dose YPEP group (HYPEP: 40 mg /kg/d YPEP). In this study, all the bone samples used were femurs. Micro-CT analysis revealed improvements in both bone mineral density (BMD) and microstructure by YPEP treatment. The three-point mechanical bending test indicated an enhancement in the biomechanical properties of the YPEP groups. The serum levels of bone alkaline phosphatase (BALP), bone gla protein (BGP), calcium (Ca), and phosphorus (P) were markedly higher in the YPEP groups than in the OVX group. The LYPEP group had markedly lower levels of alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP) and C-terminal telopeptide of type I collagen (CTX-I) than the OVX group. The YPEP groups had significantly higher protein levels of the Wnt3a, β-catenin, LRP5, RUNX2 and OPG of the Wnt/β-catenin signaling pathway compared with the OVX group. Compared to the OVX group, the ratio of OPG/RANKL was markedly higher in the LYPEP group. At the genus level, there was a significantly increase in relative abundance of Lachnospiraceae_NK4A136_group and a decrease in Escherichia_Shigella in YPEP groups, compared with the OVX group. However, in the correlation analysis, there was no correlation between these two bacteria and bone metabolism and microstructure indexes. These findings demonstrate that YPEP has the potential to improve osteoporosis, and the mechanism may be associated with its modulating effect on Wnt/β-catenin signaling pathway.

Fructooligosaccharides act on the gut-bone axis to improve bone independent of Tregs and alter osteocytes in young adult C57BL/6 female mice

Targeting the gut-bone axis with probiotics and prebiotics is considered as a promising strategy to reduce the risk of osteoporosis. Gut-derived short chain fatty acids (SCFA) mediate the effects of probiotics on bone via Tregs, but it is not known whether prebiotics act through a similar mechanism. We investigated how 2 different prebiotics, tart cherry (TC) and fructooligosaccharide (FOS), affect bone, and whether Tregs are required for this response. Eight-wk-old C57BL/6 female mice were fed with diets supplemented with 10% w/w TC, FOS, or a control diet (Con; AIN-93M) diet, and they received an isotype control or CD25 Ab to suppress Tregs. The FOS diet increased BMC, density, and trabecular bone volume in the vertebra (~40%) and proximal tibia (~30%) compared to the TC and control diets (Con), irrespective of CD25 treatment. Both prebiotics increased (P < .01) fecal SCFAs, but the response was greater with FOS. To determine how FOS affected bone cells, we examined genes involved in osteoblast and osteoclast differentiation and activity as well as genes expressed by osteocytes. The FOS increased the expression of regulators of osteoblast differentiation (bone morphogenetic protein 2 [Bmp2], Wnt family member 10b [Wnt10b] and Osterix [Osx]) and type 1 collagen). Osteoclasts regulators were unaltered. The FOS also increased the expression of genes associated with osteocytes, including (Phex), matrix extracellular phosphoglycoprotein (Mepe), and dentin matrix acidic phosphoprotein 1 (Dmp-1). However, Sost, the gene that encodes for sclerostin was also increased by FOS as the number and density of osteocytes increased. These findings demonstrate that FOS has a greater effect on the bone mass and structure in young adult female mice than TC and that its influence on osteoblasts and osteocytes is not dependent on Tregs.

Alteration in the gut microbiome is associated with changes in bone metabolism after laparoscopic sleeve gastrectomy

Laparoscopic sleeve gastrectomy (LSG), the most common bariatric surgical procedure, leads to durable weight loss and improves obesity-related comorbidities. However, it induces abnormalities in bone metabolism. One unexplored potential contributor is the gut microbiome, which influences bone metabolism and is altered after surgery. We characterized the relationship between the gut microbiome and skeletal health in severe obesity and after LSG. In a prospective cohort study, 23 adults with severe obesity underwent skeletal health assessment and stool collection preoperatively and 6 mo after LSG. Gut microbial diversity and composition were characterized using 16S rRNA gene sequencing, and fecal concentrations of short-chain fatty acids (SCFA) were measured with LC-MS/MS. Spearman's correlations and PERMANOVA analyses were applied to assess relationships between the gut microbiome and bone health measures including serum bone turnover markers (C-terminal telopeptide of type 1 collagen [CTx] and procollagen type 1 N-terminal propeptide [P1NP]), areal BMD, intestinal calcium absorption, and calciotropic hormones. Six months after LSG, CTx and P1NP increased (by median 188% and 61%, P < .01) and femoral neck BMD decreased (mean -3.3%, P < .01). Concurrently, there was a decrease in relative abundance of the phylum Firmicutes. Although there were no change in overall microbial diversity or fecal SCFA concentrations after LSG, those with greater within-subject change in gut community microbial composition (β-diversity) postoperatively had greater increases in P1NP level (ρ = 0.48, P = .02) and greater bone loss at the femoral neck (ρ = -0.43, P = .04). In addition, within-participant shifts in microbial richness/evenness (α-diversity) were associated with changes in IGF-1 levels (ρ = 0.56, P < .01). The lower the postoperative fecal butyrate concentration, the lower the IGF-1 level (ρ = 0.43, P = .04). Meanwhile, the larger the decrease in butyrate concentration, the higher the postoperative CTx (ρ = -0.43, P = .04). These findings suggest that LSG-induced gut microbiome alteration may influence skeletal outcomes postoperatively, and microbial influences on butyrate formation and IGF-1 are possible mechanisms.

Glucocorticoid-induced osteoporosis is prevented by dietary prune in female mice

Glucocorticoid-induced osteoporosis (GIO) is a significant side effect of prolonged glucocorticoid (GC) treatment. Chronic GC treatment also leads to trabecular bone loss and gut microbiota dysbiosis in mice. The gut dysbiosis is mechanistically linked to GIO, which indicates that the microbiota can be targeted to prevent GIO. Prunes, a dried fruit and prebiotic, have emerged in the literature as an effective treatment for sex-steroid deficiency induced osteoporosis (primary osteoporosis). Prunes also significantly alter the composition of the gut microbiota in both rodent models and human studies. Therefore, we tested if dietary prune (DP) supplementation could prevent GC-induced bone loss and affect microbiota composition in an established model of GIO. Sixteen-week-old, skeletally mature, female C57BL/6J mice were treated with a subcutaneous 5 mg placebo or prednisolone pellet for 8 weeks and fed an AIN-93M control diet or a diet modified to include 5, 15, or 25% (w/w) dried California prune powder. As expected, GC treated mice developed significant trabecular bone loss in the distal femur. More importantly, as little as 5% DP supplementation effectively prevented trabecular bone loss. Further, dose dependent increases in trabecular bone volume fraction were observed in GC + 15% and GC + 25% DP mice. Amazingly, in the placebo (non-GC treated) groups, 25% DP supplementation caused a ∼3-fold increase in distal femur trabecular bone volume fraction; this sizable bone response has not been previously observed in healthy mice with gut targeted natural treatments. Along with the striking effect on bone health, GC treatment and 25% DP supplementation led to drastic shifts in gut microbiota composition and several specific changes are strongly associated with bone health. Taken together, these results are the first to demonstrate that DP supplementation effectively prevents the negative effects of prolonged GC therapy on trabecular bone health and strongly associates with shifts in the composition of the gut microbiota.

Profiles of biliary microbiota in biliary obstruction patients with Clonorchis sinensis infection

Background

Clonorchis sinensis (C. sinensis) is a epidemiologically significant food-borne parasite, causing several hepatobiliary diseases. Biliary microbiota community structure might be influenced by infection with pathogens. However, the biliary microbiome of biliary obstruction patients infected with C. sinensis is still an unexplored aspect.

Methods

A total of 50 biliary obstruction patients were enrolled, including 24 infected with C. sinensis and 26 non-infected subjects. The bile samples were collected by Endoscopic Retrograde Cholangiopancretography. Biliary microbiota alteration was analyzed through high-throughput 16S ribosomal RNA (rRNA) gene sequencing.

Results

Our findings revealed that there was significant increase in both richness and diversity, as well as changes in the taxonomic composition of the biliary microbiota of C. sinensis infected patients. At the phylum level, C. sinensis infection induced Proteobacteria increased and Firmicutes reduced. At the genus level, the relative abundance of Pseudomonas and Staphylococcus increased significantly, while Enterococcus decreased prominently in infected groups (P < 0.05). The PICRUSt analysis further showed remarkably different metabolic pathways between the two groups.

Conclusion

C. sinensis infection could modify the biliary microbiota, increasing the abundance and changing the phylogenetic composition of bacterial in biliary obstruction patients. This study may help deepen the understanding of the host-biliary microbiota interplay with C. sinensis infection on the background of biliary obstruction and provide new insights into understanding the pathogenesis of clonorchiasis.

Cordymin alleviates osteoporosis induced by hindlimb unloading via regulating the gut - microelements -bone axis --for non-clinical studies

INTRODUCTION

The purpose of this study was to evaluate the protective effects of cordymin on osteoporosis induced by hindlimb unloading(HLU) in rats and whether cordymin can prevent bone loss from HLU.

MATERIALS AND METHODS

We employed the hindlimb suspension rats model to mimic physiological changes concomitant with space travel.The mechanical strength in the femoral neck,cancellous bone volume, gut microbiota structure,serum calcium and phosphorus contents, bone mineral content and bone mineral content can be changed after hindlimb unloading. Oral cordymin was administered for 4 weeks,cordymin treatment significantly increased the mechanical strength through elevated bone volume/tissue volume (BV/TV), trabecular number (Tb. N), trabecular thickness (Tb. Th) and decreased trabecular separation (Tb. Sp).

RESULTS

Importantly, 16 S rRNA sequencing showed cordymin treatment regulated the various genera that were imbalanced in hindlimb unloading rats. At the same time,The plasma total calcium and inorganic phosphate concentrations in hindlimb unloading rats decreased and bone mineral content in the lumbar vertebrae and femur increased after treatment with cordymin.

CONCLUSION

These data indicate that the cordymin might exert bone protective effects indirectly via modulating the complex relationship between gut microbiota, microelements and bone loss.

Lactobacillus Reuteri 6475 Prevents Bone Loss in a Clinically Relevant Oral Model of Glucocorticoid-Induced Osteoporosis in Male CD-1 Mice

Glucocorticoids (GCs) are commonly used anti-inflammatory medications with significant side effects, including glucocorticoid-induced osteoporosis (GIO). We have previously demonstrated that chronic subcutaneous GC treatment in mice leads to gut barrier dysfunction and trabecular bone loss. We further showed that treating with probiotics or barrier enhancers improves gut barrier function and prevents GIO. The overall goal of this study was to test if probiotics could prevent GC-induced gut barrier dysfunction and bone loss in a clinically relevant oral-GC model of GIO. Eight-week-old male CD-1 mice were treated with vehicle or corticosterone in the drinking water for 4 weeks and administered probiotics Lactobacillus reuteri ATCC 6475 (LR 6475) or VSL#3 thrice weekly via oral gavage. As expected, GC treatment led to significant gut barrier dysfunction (assessed by measuring serum endotoxin levels) and bone loss after 4 weeks. Serum endotoxin levels significantly and negatively correlated with bone volume. Importantly, LR 6475 treatment effectively prevented both GC-induced increase in serum endotoxin and trabecular bone loss. VSL#3 had intermediate results, not differing from either control or GC-treated animals. GC-induced reductions in femur length, cortical thickness, and cortical area were not affected by probiotic treatment. Taken together, these results are the first to demonstrate that LR 6475 effectively prevents the detrimental effects of GC treatment on gut barrier, which correlates with enhanced trabecular bone health in an oral mouse model of GIO. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Neuropeptide Y-Mediated Gut Microbiota Alterations Aggravate Postmenopausal Osteoporosis

Postmenopausal osteoporosis (PMO) is often accompanied by neuroendocrine changes in the hypothalamus, which closely associates with the microbial diversity, community composition, and intestinal metabolites of gut microbiota (GM). With the emerging role of GM in bone metabolism, a potential neuroendocrine signal neuropeptide Y (NPY) mediated brain-gut-bone axis has come to light. Herein, it is reported that exogenous overexpression of NPY reduced bone formation, damaged bone microstructure, and up-regulated the expressions of pyroptosis-related proteins in subchondral cancellous bone in ovariectomized (OVX) rats, but Y1 receptor antagonist (Y1Ra) reversed these changes. In addition, it is found that exogenous overexpression of NPY aggravated colonic inflammation, impaired intestinal barrier integrity, enhanced intestinal permeability, and increased serum lipopolysaccharide (LPS) in OVX rats, and Y1Ra also reversed these changes. Most importantly, NPY and Y1Ra modulated the microbial diversity and changed the community composition of GM in OVX rats, and thereby affecting the metabolites of GM (e.g., LPS) entering the blood circulation. Moreover, fecal microbiota transplantation further testified the effect of NPY-mediated GM changes on bone. In vitro, LPS induced pyroptosis, reduced viability, and inhibited differentiation of osteoblasts. The study demonstrated the existence of NPY-mediated brain-gut-bone axis and it might be a novel emerging target to treat PMO.

Gut microbiota impacts bone via Bacteroides vulgatus-valeric acid-related pathways

Although the gut microbiota has been reported to influence osteoporosis risk, the individual species involved, and underlying mechanisms, remain largely unknown. We performed integrative analyses in a Chinese cohort of peri-/post-menopausal women with metagenomics/targeted metabolomics/whole-genome sequencing to identify novel microbiome-related biomarkers for bone health. Bacteroides vulgatus was found to be negatively associated with bone mineral density (BMD), which was validated in US white people. Serum valeric acid (VA), a microbiota derived metabolite, was positively associated with BMD and causally downregulated by B. vulgatus. Ovariectomized mice fed B. vulgatus demonstrated increased bone resorption and poorer bone micro-structure, while those fed VA demonstrated reduced bone resorption and better bone micro-structure. VA suppressed RELA protein production (pro-inflammatory), and enhanced IL10 mRNA expression (anti-inflammatory), leading to suppressed maturation of osteoclast-like cells and enhanced maturation of osteoblasts in vitro. The findings suggest that B. vulgatus and VA may represent promising targets for osteoporosis prevention/treatment.

The causal relationship between gut microbiota and bone mineral density: a Mendelian randomization study

Background

The gut microbiota has emerged as an intriguing and potentially influential factor in regulating bone health. However, the causal effect of the gut microbiota on bone mineral density (BMD) appears to differ throughout various life stages.

Methods

We conducted a Mendelian randomization (MR) analysis to investigate the potential causal relationship between gut microbiota and BMD in five distinct age groups: 0-15, 15-30, 30-45, 45-60, and 60 years and older. The analysis employed three different methods, namely MR-Egger, weighted median, and Inverse-variance weighting, to ensure the robustness of our findings, a series of sensitivity analyses were also conducted, such as horizontal pleiotropy tests, heterogeneity tests, and leave-one-out sensitivity tests.

Results

In the age group of 0-15 years, Eubacterium_fissicatena_group and Eubacterium_hallii_group were identified as risk factors for BMD. During the 15-30 age group, Phascolarctobacterium, Roseburia, and Ruminococcaceae_UCG_003 were found to be protective factors for BMD. In the 30-45 age group, Lachnospira genus demonstrated a protective effect on BMD, while Barnesiella and Lactococcus were identified as risk factors for BMD. Moving on to the 45-60 age group, Eubacterium_ventriosum_group, Lachnospiraceae_UCG_004, and Subdoligranulum were observed to be protective factors for BMD, while Eubacterium_coprostanoligenes_group, Fusicatenibacter, and Lactococcus were associated with an increased risk of BMD. In individuals aged 60 years and older, Fusicatenibacter and Ruminococcaceae_UCG_002 were also noted as risk factors for BMD. Conversely, Eubacterium_ruminantium_group, Ruminococcus_gauvreauii_group, Alistipes, and Coprococcus_3 were found to be protective factors for BMD, whereas Barnesiella and Sellimonas were identified as risk factors for BMD.

Conclusion

A robust causal relationship between gut microbiota and bone mineral density (BMD) exists throughout all stages of life, with Firmicutes phylum being the primary group associated with BMD across age groups. Gut microbiota linked with BMD primarily belong to the Firmicutes phylum across age groups. The diversity of gut microbiota phyla associated with BMD depicts relatively stable patterns during the ages of 0-45 years. However, for individuals aged 45 years and above, there is an observed increase in the number of gut microbiota species linked with BMD, and by the age of 60 years, a trend toward an increase in the Bacteroidetes phylum categories is proposed.

Advancing our understanding of the influence of drug induced changes in the gut microbiome on bone health

The gut microbiome has been implicated in a multitude of human diseases, with emerging evidence linking its microbial diversity to osteoporosis. This review article will explore the molecular mechanisms underlying perturbations in the gut microbiome and their influence on osteoporosis incidence in individuals with chronic diseases. The relationship between gut microbiome diversity and bone density is primarily mediated by microbiome-derived metabolites and signaling molecules. Perturbations in the gut microbiome, induced by chronic diseases can alter bacterial diversity and metabolic profiles, leading to changes in gut permeability and systemic release of metabolites. This cascade of events impacts bone mineralization and consequently bone mineral density through immune cell activation. In addition, we will discuss how orally administered medications, including antimicrobial and non-antimicrobial drugs, can exacerbate or, in some cases, treat osteoporosis. Specifically, we will review the mechanisms by which non-antimicrobial drugs disrupt the gut microbiome's diversity, physiology, and signaling, and how these events influence bone density and osteoporosis incidence. This review aims to provide a comprehensive understanding of the complex interplay between orally administered drugs, the gut microbiome, and osteoporosis, offering new insights into potential therapeutic strategies for preserving bone health.

Causal Link between Gut Microbiota, Neurophysiological States, and Bone Diseases: A Comprehensive Mendelian Randomization Study

Increasing evidence highlights a robust correlation between the gut microbiota and bone diseases; however, the existence of a causal relationship between them remains unclear. In this study, we thoroughly examined the correlation between gut microbiota and skeletal diseases using genome-wide association studies. Linkage disequilibrium score regression and Mendelian randomization were used to probe genetic causality. Furthermore, the potential mediating role of neuropsychological states (i.e., cognition, depression, and insomnia) between the gut microbiota and bone diseases was evaluated using mediation analysis, with genetic colocalization analysis revealing potential targets. These findings suggest a direct causal relationship between Ruminococcaceae and knee osteoarthritis (OA), which appears to be mediated by cognitive performance and insomnia. Similarly, a causal association was observed between Burkholderiales and lumbar pelvic fractures, mediated by cognitive performance. Colocalization analysis identified a shared causal variant (rs2352974) at the TRAF-interacting protein locus for cognitive ability and knee OA. This study provides compelling evidence that alterations in the gut microbiota can enhance cognitive ability, ameliorate insomnia, and potentially reduce the risk of site-specific fractures and OA. Therefore, strategies targeting gut microbiota optimization could serve as novel and effective preventive measures against fractures and OA.

Effects of Periodontitis on Major Organ Systems

This review focuses on the fact that oral disorders are not merely localized to the mouth; in a broader sense, they also have a more significant impact on systemic health. In this review, we tried to bring to the notice various complications of periodontitis on the body's major organ systems. It has also been suggested that there is a potential connection between periodontitis and certain systemic disorders. Reviewing this fascinating topic is necessary. The objective is to create a thorough body of knowledge on the subject that is simple to access, alert medical professionals to the connection between dental health and systemic health, and highlight the necessity of a more thorough incorporation of medical and dental training. Periodontitis is a probable risk factor for various problems connected to the cardiovascular, pulmonary, endocrine, musculoskeletal, central nervous, and reproductive systems. It is a continual likely source of infection. Oral health affects overall health, and if extensive healthcare is ever accomplished, dental health should never be considered a distinct, remote, and lower significant part of health wholly disconnected from quality of life. One should never underestimate oral disorders as being acute and always curable. People should take utmost care and take the condition seriously to prevent significant complications.

Microenvironment of the Lower Reproductive Tract: Focus on the Cervical Mucus Plug

The female lower reproductive tract microbiota is a complex ecosystem comprising various microorganisms that play a pivotal role in maintaining women's reproductive well-being. During pregnancy, the vaginal microbiota undergoes dynamic changes that are important for a successful gestation. This review summarizes the implications of the cervical mucus plug microenvironment and its profound impact on reproductive health. Further, the symbiotic relationship between the vaginal microbiome and the cervical mucus plug is highlighted, with a special emphasis on how this natural barrier serves as a guardian against ascending infections. Understanding this complex host-microbes interplay could pave the way for innovative approaches to improve women's reproductive health and fertility.

Initial Development of an Immediate Implantation Model in Rats and Assessing the Prognostic Impact of Periodontitis on Immediate Implantation

BACKGROUND

To establish an immediate implantation rat model and to evaluate the effects of pre-existing periodontitis and two different socket rinse solutions on immediate implantation prognosis.

METHODS

Sprague-Dawley (SD) rats were randomly divided into three groups before immediate implantation, including the control group, the group with experimentally induced periodontitis (EP), in which rats have been experimentally induced periodontitis before implantation, and the group with induced periodontitis and with extraction sockets rinsed with three percent H2O2 (EP-H2O2), in which rats have been induced periodontitis before implantation, and extraction sockets were rinsed with three percent H2O2. Periodontitis was induced by ligating the thread around the molars for four weeks. Six weeks after titanium alloy implants were self-tapped and left to heal transmucosally, maxillae were dissected after the clinical examination to perform micro-CT and histological analysis.

RESULTS

An immediate implantation model was successfully built in rats. There was no significant difference in implant survival rates between the EP and control groups. However, the clinical examination results, micro-CT analysis, and histological analysis in EP and EP-H2O2 groups showed a significantly worse prognosis than in the control group. Three percent H2O2 showed a similar effect with saline.

CONCLUSION

This study presented a protocol for establishing a rat immediate implantation model and showed that periodontitis history might negatively affect the prognosis of immediate implantation. These findings urge caution and alternative strategies for patients with periodontal disease history, enhancing the long-term success of immediate implantation in dental practice. Additionally, the comparable outcomes between 3% H2O2 and saline suggest the use of saline as a cost-effective and safer alternative for implant site preparation in dental practice.

A review of Duhuo Jisheng decoction mechanisms in intervertebral disc degeneration in vitro and animal studies

Intervertebral disc degeneration (IVDD) has become a serious public health problem, placing a heavy burden on society and the healthcare system. Its pathogenesis is not completely clear and may be closely related to mechanical damage, inflammatory factors, oxidative stress and death of nucleus pulposus cells (NPCs). The treatment of IVDD mainly includes conservative treatment and surgery. Conservative treatment is based on hormonal and anti-inflammatory drugs and massage techniques, which can relieve the pain symptoms to a certain extent, but cannot solve the problem from the root cause. Surgical treatment is mainly by removing the herniated nucleus pulposus, but it is more traumatic for IVDD patients, expensive and not suitable for all patients. Therefore, it is extremely important to clarify the pathogenesis of IVDD, to find an effective and convenient treatment and to further elaborate its mechanism of action. The effectiveness of traditional Chinese medicine in the treatment of IVDD has been well demonstrated in clinical medical research. We have been working on the Chinese herbal formula Duhuo Jisheng Decoction, which is a common formula for the treatment of degenerative disc disease. Not only does it have significant clinical effects, but it also has few adverse effects. At present, we found that its mechanism of action mainly involves regulation of inflammatory factors, reduction of apoptosis and pyroptosis of NPCs, inhibition of extracellular matrix degradation, improvement of intestinal flora, etc. However, a few relevant articles have yet comprehensively and systematically summarized the mechanisms by which they exert their effect. Therefore, this paper will comprehensively and systematically explain on it. This is of great clinical significance and social value for elucidating the pathogenesis of IVDD and improving the symptoms of patients, and will provide a theoretical basis and scientific basis for the treatment of IVDD with traditional Chinese medicine.

Linking the relation between gut microbiota and glucocorticoid-induced osteoporosis

Osteoporosis (OP) is the most prevalent metabolic bone disease, characterized by the low bone mass and microarchitectural deterioration of bone tissue. Glucocorticoid (GC) clinically acts as one of the anti-inflammatory, immune-modulating, and therapeutic drugs, whereas the long-term use of GC may cause rapid bone resorption, followed by prolonged and profound suppression of bone formation, resulting in the GC-induced OP (GIOP). GIOP ranks the first among secondary OP and is a pivotal risk for fracture, as well as high disability rate and mortality, at both societal and personal levels, vital costs. Gut microbiota (GM), known as the "second gene pool" of human body, is highly correlated with maintaining the bone mass and bone quality, and the relation between GM and bone metabolism has gradually become a research hotspot. Herein, combined with recent studies and based on the cross-linking relationship between GM and OP, this review is aimed to discuss the potential mechanisms of GM and its metabolites on the OP, as well as the moderating effects of GC on GM, thereby providing an emerging thought for prevention and treatment of GIOP.

Autologous Tooth Graft: Innovative Biomaterial for Bone Regeneration. Tooth Transformer® and the Role of Microbiota in Regenerative Dentistry. A Systematic Review

Different biomaterials, from synthetic products to autologous or heterologous grafts, have been suggested for the preservation and regeneration of bone. The aim of this study is to evaluate the effectiveness of autologous tooth as a grafting material and examine the properties of this material and its interactions with bone metabolism. PubMed, Scopus, Cochrane Library, and Web of Science were searched to find articles addressing our topic published from 1 January 2012 up to 22 November 2022, and a total of 1516 studies were identified. Eighteen papers in all were considered in this review for qualitative analysis. Demineralized dentin can be used as a graft material, since it shows high cell compatibility and promotes rapid bone regeneration by striking an ideal balance between bone resorption and production; it also has several benefits, such as quick recovery times, high-quality newly formed bone, low costs, no risk of disease transmission, the ability to be performed as an outpatient procedure, and no donor-related postoperative complications. Demineralization is a crucial step in the tooth treatment process, which includes cleaning, grinding, and demineralization. Since the presence of hydroxyapatite crystals prevents the release of growth factors, demineralization is essential for effective regenerative surgery. Even though the relationship between the bone system and dysbiosis has not yet been fully explored, this study highlights an association between bone and gut microbes. The creation of additional scientific studies to build upon and enhance the findings of this study should be a future objective of scientific research.

Dietary Fiber Intake Influences Changes in Ankylosing Spondylitis Disease Status

The objectives of this study were to characterize dietary fiber (DF) intake in patients with ankylosing spondylitis (AS), to assess whether DF intake affects disease activity in AS, and to investigate the effect of DF intake on disease activity in AS in the context of functional bowel disease (FBD) symptoms. We recruited 165 patients with AS and divided them into two groups according to whether they had a high DF intake > 25 g/d to investigate the characteristics of people with high DF intake. Some 72 of the 165 AS patients (43%) met the criteria for high DF intake, which was more common in patients with negative FBD symptoms (68%). Data analysis revealed that DF intake was negatively associated with AS disease activity and did not differ statistically significantly from FBD symptoms. Multivariate adjusted models were used to explore the effect of DF intake on AS disease activity. ASDAS-CRP and BASDAI were stable and negatively correlated across models in both groups with and without FBD symptoms. Thus, DF intake positively affected disease activity in patients with AS. ASDAS-CRP and BASDAI were negatively correlated with DF intake.

Fracture Risk in Vegetarians and Vegans: the Role of Diet and Metabolic Factors

PURPOSE OF REVIEW

There is strong evidence that poor dietary intake of certain micro- and macro-nutrients can negatively affect bone health. It is unclear if diet is the primary culprit for poor bone health in the vegan population.

RECENT FINDINGS

Plant-based diets are gaining public interest since they may improve metabolic health. Studies that examine vegetarians and vegans together show a lower bone mineral density (BMD), but not always increased fracture risk compared to omnivores. However, vegans consistently have higher risk of fracture at multiple bone sites, especially at the hip. There is higher fracture risk in vegans which may be due to calcium and vitamin D intake, as well as amount of dietary protein and quality. Other nutrients (B vitamins, Se, Zn, Fe, iodine) or physiological factors (lower body mass index, microbiome, or endocrine profile) may also play a role but have not been examined and require further study.

Combination of Cinnamaldehyde with Carvacrol or Thymol Improves the Mechanical Properties of Tibia in Post-Peak Laying Hens

Roles of plant-derived cinnamaldehyde, carvacrol, and thymol in the gut and bone health of laying hens was evaluated in the present study. After acclimation for 2 weeks, a total 384 of 52-week-old laying hens were allocated into three groups for 6 weeks: (1) basal diet group (Ctrl), (2) combination of cinnamaldehyde with carvacrol group (CAR+CIN), and (3) blend of cinnamaldehyde with thymol (THY+CIN). The dietary essential oil level was 100 mg/kg. Each treatment group had eight replicate pens (16 birds/pen). The stiffness and ultimate load of the tibiae from both the CAR+CIN and THY+CIN groups were higher than that of the Ctrl group (p < 0.05), along with comparable tibia ash, calcium, and phosphorus content among groups. At the same time, the manipulation of essential oils upregulated the transcription abundances of intestinal barrier proteins to varying degrees, whereas the experimental treatment failed to affect the composition in phyla of cecal microbiota. When compared to the Ctrl group, birds fed the CAR+CIN and THY+CIN diet displayed decreased bone resorption markers, reduced interleukin-1 concentrations, and increased transforming growth factor beta levels in serum. These findings suggest that cinnamaldehyde with carvacrol or thymol in feed of hens could enhance intestinal barrier and improve the mechanical properties of tibiae through structural modelling but not increase the mineral density, which might be involved in suppressing inflammation-mediated bone resorption.

A narrative review of the moderating effects and repercussion of exercise intervention on osteoporosis: ingenious involvement of gut microbiota and its metabolites

Osteoporosis (OP) is a systemic bone disease characterized by the decreased bone mass and destruction of bone microstructure, which tends to result in the enhanced bone fragility and related fractures, as well as high disability rate and mortality. Exercise is one of the most common, reliable and cost-effective interventions for the prevention and treatment of OP currently, and numerous studies have revealed the close association between gut microbiota (GM) and bone metabolism recently. Moreover, exercise can alter the structure, composition and abundance of GM, and further influence the body health via GM and its metabolites, and the changes of GM also depend on the choice of exercise modes. Herein, combined with relevant studies and based on the inseparable relationship between exercise intervention-GM-OP, this review is aimed to discuss the moderating effects and potential mechanisms of exercise intervention on GM and bone metabolism, as well as the interaction between them.

Targeting the Gut Microbiome for Inflammation and Pain Management in Orthopedic Conditions

The human gut microbiome can be altered with probiotics, prebiotics, synbiotics, and anti-inflammatory foods and spices as part of an evidence-based strategy that targets inflammation and pain in common orthopedic conditions. Implementing these strategies avoids adverse effects associated with nonsteroidal anti-inflammatory drugs and minimizes the potential for opioid use. This review focuses exclusively on human trials studying the effects of gut microbiome alterations to address pain and inflammatory markers in common orthopedic conditions: osteoarthritis, rheumatoid arthritis, fractures/osteoporosis, and bone pain associated with chemotherapy. Individualized supplementation strategies can be further explored with the information in this review. [Orthopedics. 2022;45(5):e226-e234.].

Gut microbiota can affect bone quality by regulating serum estrogen levels

Germ-free (GF) animals and animal models of the antibiotic disruption of gut microbiota are widely used to explore studies of gut microbiota-host interactions. The role of gut microbiota in bone growth and development has been well explained in studies on GF mice, indicating that changes in the gut microbiota may affect normal bone developmental processes. The mechanisms, however, are yet unclear. This study aims to clarify the effect of antibiotic treatment disrupting the gut microbiota on bone development in mice and investigate the possible causes of this effect. Our results show that long-term antibiotic feeding significantly alters gut microbiota composition in mice, reduces the bone mineral density of the spinal region, and leads to changes in trabecular microstructure. Interestingly, we found a significant decrease in the serum estrogen levels in mice treated with antibiotics, suggesting that gut microbiota may affect bone quality by regulating serum estrogen levels. These results may help understand how gut ecological dysregulation affects sex hormones and provide a new conception for the clinical treatments of osteoporosis.

Salivary microbiota of periodontitis aggravates bone loss in ovariectomized rats

The mechanisms underlying the crosstalk between periodontitis and osteoporosis remain unclear. Recently, the gut microbiota has been recognized as a pivotal regulator of bone metabolism, and oral and gut mucosae are microbiologically connected. In this study, we investigated the effects of periodontitis on osteoporosis through the oral-gut axis. The salivary microbiota of patients with periodontitis was collected and then pumped into the intestine of Sprague–Dawley rats via intragastric administration for 2 weeks. An osteoporosis model was established using ovariectomy. Changes in the maxillae and femora were evaluated using microcomputed tomography (micro CT) and HE staining. Intestinal barrier integrity and inflammatory factors were examined using real-time quantitative polymerase chain reaction and immunofluorescence. The gut microbiota was profiled by 16S rRNA gene sequencing. Metabolome profiling of serum was performed using liquid chromatography-mass spectrometry sequencing. Micro CT and HE staining revealed osteoporotic phenotypes in the maxillae and femora of ovariectomized (OVX) rats. Our results confirmed that the salivary microbiota of patients with periodontitis aggravated femoral bone resorption in OVX rats. In addition, intestinal inflammation was exacerbated after periodontitis salivary microbiota gavage in OVX rats. Correlation analysis of microbiota and metabolomics revealed that lipolysis and tryptophan metabolism may be related to the bone loss induced by the salivary microbiota of patients with periodontitis. In conclusion, periodontitis can aggravate long bone loss through the oral-gut axis in OVX rats.

Association of serum 25-hydroxyvitamin D (25(OH)D) levels with the gut microbiota and metabolites in postmenopausal women in China

Background

Vitamin D insufficiency or deficiency is associated with an altered microbiota in older men. However, the relationship between the gut microbiota and 25-hydroxyvitamin D (25(OH)D) levels remains unknown in postmenopausal women. In this study, fecal microbiota profiles for 88 postmenopausal women in the high 25(OH)D (HVD) group (n = 44) and the low 25(OH)D (LVD) group (n = 44) were determined. An integrated 16S rRNA gene sequencing and liquid chromatography–mass spectrometry (LC–MS)-based metabolomics approach was applied to explore the association of serum 25(OH)D levels with the gut microbiota and fecal metabolic phenotype. Adjustments were made using several statistical models for potential confounding variables identified from the literature.

Results

The results demonstrated that the community diversity estimated by the Observe, Chao1 and ACE indexes was significantly lower in the LVD group than in the HVD group. Additionally, two kinds of characteristic differences in the microflora were analyzed in the HVD group, and ten kinds of characteristic differences in the microflora were analyzed in the LVD group. We observed that some bacteria belonging to the genera Bifidobacterium, Bacillus, F0332 and Gemella, were enriched in the LVD group, as were other genera, including Lachnoclostridium, UC5_1_2E3, Ruminococcus_gnavus_group and un_f_Lachnospiraceae. Christensenellaceae, Eggerthellaceae and Cloacibacillus were enriched in the HVD group. The L-pyroglutamic acid, inosine, and L-homocysteic acid levels were higher in the HVD group and were negatively correlated with the 1,2-benzenedicarboxylic acid and cholic acid metabolic levels.

Conclusions

These observations provide a better understanding of the relationships between serum 25(OH)D levels and the fecal microbiota and metabolites in postmenopausal women.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01858-6.

New Advances in Improving Bone Health Based on Specific Gut Microbiota

The gut microbiota has been shown to play an important role in the pathogenesis of various diseases, including metabolic diseases, cardiovascular diseases, and cancer. Recent studies suggest that the gut microbiota is also closely associated with bone metabolism. However, given the high diversity of the gut microbiota, the effects of different taxa and compositions on bone are poorly understood. Previous studies demonstrated that the mechanisms underlying the effects of the gut microbiota on bone mainly include its modulation of nutrient absorption, intestinal permeability, metabolites (such as short-chain amino acids), immune responses, and hormones or neurotransmitters (such as 5-hydroxytryptamine). Several studies found that external interventions, such as dietary changes, improved bone health and altered the composition of the gut microbiota. This review summarises the beneficial gut bacteria and explores how dietary, natural, and physical factors alter the diversity and composition of the gut microbiota to improve bone health, thereby providing potential new insight into the prevention of osteoporosis.

Effects of Intestinal Flora on Irritable Bowel Syndrome and Therapeutic Significance of Polysaccharides

In recent years, the relevant research on intestinal flora has been in full swing, and it has become an extremely important research direction in clinical medicine and life science. Irritable bowel syndrome (IBS) is a common disease characterized by changes in intestinal function and accompanied by comorbid anxiety. At present, the pathogenic mechanism of IBS is not yet clear. The gut-brain axis (GBA), as a two-way information exchange system between the gut and the brain, has an important influence on the prevention of IBS. Present studies have shown that polysaccharides are important for maintaining the steady status of intestinal micro-environment. This review summarized the relationship between intestinal flora, GBA and immune activation, and provided a new idea for the preventive treatment of IBS from the perspective of polysaccharides.

Integrated Fecal Microbiome and Metabolomics Reveals a Novel Potential Biomarker for Predicting Tibial Dyschondroplasia in Chickens

Tibial dyschondroplasia (TD) is a metabolic tibial-tarsal disorder occurring in fast-growing poultry, and its diagnosis is mainly based on an invasive method. Here, we profiled the fecal gut microbiome and metabolome of broilers with and without TD to identify potential non-invasive and non-stress biomarkers of TD. First, TD broilers with the most pronounced clinical signs during the experiment were screened and faecal samples were collected for integrated microbiome and metabolomics analysis. Moreover, the diagnostic potential of identified biomarkers was further validated throughout the experiment. It was noted that the microbial and metabolic signatures of TD broilers differed from those of normal broilers. TD broilers were characterized by enriched bacterial OTUs of the genus Klebsiella, and depleted genera [Ruminococcus], Dorea, Ruminococcus, Oscillospira, Ochrobactrum, and Sediminibacterium. In addition, a total of 189 fecal differential metabolites were identified, mainly enriched in the purine, vitamin and amino acid metabolism, which were closely associated with differential microbiota and tibia-related indicators. Furthermore, three fecal metabolites were screened, including 4-hydroxybenzaldehyde, which distinguished TD from normal broilers with extremely high specificity and was superior to serum bone markers. These results indicated that gut microbiota equilibrium might influence the pathogenesis of TD by modulating host metabolism, and the identified fecal metabolite 4-hydroxybenzaldehyde might be a potential and non-invasive biomarker for predicting TD in chickens.

Mogrol Attenuates Osteoclast Formation and Bone Resorption by Inhibiting the TRAF6/MAPK/NF-κB Signaling Pathway In vitro and Protects Against Osteoporosis in Postmenopausal Mice

Osteoporosis is a serious public health problem that results in fragility fractures, especially in postmenopausal women. Because the current therapeutic strategy for osteoporosis has various side effects, a safer and more effective treatment is worth exploring. It is important to examine natural plant extracts during new drug design due to low toxicity. Mogrol is an aglycon of mogroside, which is the active component of Siraitia grosvenorii (Swingle) and exhibits anti-inflammatory, anticancer and neuroprotective effects. Here, we demonstrated that mogrol dose-dependently inhibited osteoclast formation and function. To confirm the mechanism, RNA sequencing (RNA-seq), real-time PCR (RT–PCR), immunofluorescence and Western blotting were performed. The RNA-seq data revealed that mogrol had an effect on genes involved in osteoclastogenesis. Furthermore, RT–PCR indicated that mogrol suppressed osteoclastogenesis-related gene expression, including CTSK, ACP5, MMP9 and DC-STAMP, in RANKL-induced bone marrow macrophages Western blotting demonstrated that mogrol suppressed osteoclast formation by blocking TNF receptor-associated factor 6 (TRAF6)-dependent activation of the mitogen-activated protein kinase nuclear factor-B (NF-κB) signaling pathway, which decreased two vital downstream transcription factors, the nuclear factor of activated T cells calcineurin-dependent 1 (NFATc1) and c-Fos proteins expression. Furthermore, mogrol dramatically reduced bone mass loss in postmenopausal mice. In conclusion, these data showed that mogrol may be a promising procedure for osteoporosis prevention or therapy.

Dietary Resistant Starch From Potato Regulates Bone Mass by Modulating Gut Microbiota and Concomitant Short-Chain Fatty Acids Production in Meat Ducks

Gut microbiota interfered with using prebiotics may improve bone mass and alleviate the onset of bone problems. This study aimed to investigate the beneficial effect of resistant starch from raw potato starch (RPS) on bone health in meat ducks. Response to the dietary graded level of RPS supplementation, both tibia strength and ash were taken out linear and quadratic increase and positively correlated with increased propionate and butyrate levels in cecal content. Moreover, further outcomes of gut microbiota and micro-CT analysis showed the beneficial effect of RPS on bone mass might be associated with higher Firmicutes proportion and the production of short-chain fatty acids (SCFAs) in the cecum. Consistent with improving bone mass, SCFAs promoted phosphorus absorption, decreased the digestive tract pH, and enhanced intestinal integrity, which decreased the expression of pro-inflammatory genes in both gut and bone marrow, and consequently depressed osteoclastic bone resorption mediated by inflammatory cytokines. These findings highlight the importance of the "gut-bone" axis and provide new insight into the effect of prebiotics on bone health.

Analysis of the Associations Between the Human Fecal Microbiome and Bone Density, Structure, and Strength: The Osteoporotic Fractures in Men (MrOS) Cohort

In preclinical models, the composition and function of the gut microbiota have been linked to bone growth and homeostasis, but there are few available data from studies of human populations. In a hypothesis-generating experiment in a large cohort of community-dwelling older men (n = 831; age range, 78-98 years), we explored the associations between fecal microbial profiles and bone density, microarchitecture, and strength measured with total hip dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HRpQCT) (distal radius, distal and diaphyseal tibia). Fecal samples were collected and the 16S rRNA gene V4 hypervariable region sequenced. Sequences were bioinformatically processed through the DADA2 pipeline and then taxonomically assigned using SILVA. Generalized linear models as implemented in microbiome multivariable association with linear models (MaAsLin 2) were used to test for associations between skeletal measures and specific microbial genera. The abundances of four bacterial genera were weakly associated with bone density, structure, or strength (false discovery rate [FDR] ≤ 0.05), and the measured directions of associations of genera were generally consistent across multiple bone measures, supporting a role for microbiota on skeletal homeostasis. However, the associated effect sizes were small (log2 fold change < ±0.35), limiting power to confidently identify these associations even with high resolution skeletal imaging phenotypes, and we assessed the resulting implications for the design of future cohort-based studies. As in analogous examples from genomewide association studies, we find that larger cohort sizes will likely be needed to confidently identify associations between the fecal microbiota and skeletal health relying on 16S sequencing. Our findings bolster the view that the gut microbiome is associated with clinically important measures of bone health, while also indicating the challenges in the design of cohort-based microbiome studies. © 2022 American Society for Bone and Mineral Research (ASBMR).

Gut Microbiome Signature Are Correlated With Bone Mineral Density Alterations in the Chinese Elders

Objective

Osteoporosis (OP), clinically featured with a low bone mineral density (BMD) and high risk of bone fracture, has become a major risk factor of disability and death in the elders, especially in postmenopausal women. The gut microbiome (GM) is thought to be implicated in bone metabolism. Herein, we clarified the composition signature and gene functional profile of GM in older people with normal and low BMD.

Design and Methods

A total of 455 participants underwent the BMD measurement and biochemical detection. GM analysis was further performed on 113 cases of postmenopausal women and men aged over 50, including both 16S rRNA and metagenomic sequencing.

Results

Generally, the BMD value was significantly lower in the older age groups, especially in the postmenopausal women. Consistently, we observed obvious vitamin D deficiency or insufficiency in females (compared to the male, P < 0.0001). The results from 16S rRNA sequencing revealed higher numbers of OTUs and diversity indexes in females than in males. The abundance in composition of Firmicutes and Clostridiales were correlated with the BMD values in females. LEfSe analysis discovered several enriched bacteria taxons in OP and normal control (NC) subgroups. A positive correlation between the number of genes and BMD values was observed in females based on metagenomic sequencing analysis. Furthermore, we identified the connecting modules among the GM composition – gene functional signature – BMD value/T score in both females and males.

Conclusions

This study provides evidences upon which to understand the mechanisms of the effects of GM on bone health, consequently revealing the physiology status and potential diagnostic/therapeutic targets based on GM for OP and postmenopausal osteoporosis (PMOP). Besides, the status of vitamin D deficiency or insufficiency need to be concerned and improved in the Chinese people.

Comparative Analysis of the Bioactive Compounds in Chicken Cartilage: Protective Effects of Chondroitin Sulfate and Type II Collagen Peptides Against Osteoarthritis Involve Gut Microbiota

This study was designed to explore osteoarthritis (OA) treatment from bioactive compounds of chicken cartilage food supplements. The OA rat model induced by sodium iodoacetate was used to evaluate the treatment effect in vivo. In this study, we used animal experiments to show that oral chondroitin sulfate (CS), cartilage powder, and type II collagen peptides could increase the athletic ability of rats and reduce inflammatory cytokine levels in serum or synovial fluid, including prostaglandin E2, tumor necrosis factor-α, interleukin (IL) 1β, IL-6, and IL-17. CS displayed the best treatment effect against OA. The morphological structure of articular cartilage indicated that CS could significantly improve cartilage tissue morphology and reduce OA score. Oral CS slowed down the development of OA by modulating gut microbiota. These results provided a useful scientific basis for the high-value utilization of chicken cartilage.

Effects of High-Fructose Corn Syrup on Bone Health and Gastrointestinal Microbiota in Growing Male Mice

Here, we explored the correlation between gut microbiota and bone health and the effects of high-fructose corn syrup (HFCS) on both. Sixteen 3-week-old male C57BL/6J mice were randomly divided into two groups and given purified water (control group) or 30% HFCS in water (HFCS group) for 16 weeks. The effects of HFCS were assessed via enzyme-linked immunosorbent assays, histopathological assays of colon and bone, and 16S rDNA sequence analysis of gut microbiota. The serum of HFCS group mice had lower levels of bone alkaline phosphatase (BALP), bone Gla protein (BGP), insulin-like growth factor 1 (IGF-1), and testosterone, and higher levels of type I collagen carboxyl-terminal telopeptide (ICTP) and tartrate-resistant acid phosphatase (TRAP) than that of the control group. HFCS caused trabecular bone damage by decreasing trabecular number and thickness and increasing trabecular separation. The HFCS group colons were shorter than the control group colons. The HFCS-fed mice showed mild, localized shedding of epithelial cells in the mucosal layer, focal lymphocytic infiltration of the lamina propria, mild submucosal edema, and loosely arranged connective tissue. The HFCS group displayed lower abundance and altered composition of gut microbiota. The abundance of Defluviitaleaceae UCG-011, Erysipelatoclostridium, Ruminococcaceae UCG-009, Lactobacillus, Blautia, and Parasutterella increased, positively correlating with BALP, BGP, IGF-1, and testosterone levels, and negatively correlating with ICTP and TRAP levels. Our study revealed a potential diet-gut microbiota-bone health axis.

Prebiotic to Improve Calcium Absorption in Postmenopausal Women After Gastric Bypass: A Randomized Controlled Trial

CONTEXT

The adverse skeletal effects of Roux-en-Y gastric bypass (RYGB) are partly caused by intestinal calcium absorption decline. Prebiotics, such as soluble corn fiber (SCF), augment colonic calcium absorption in healthy individuals.

OBJECTIVE

We tested the effects of SCF on fractional calcium absorption (FCA), biochemical parameters, and the fecal microbiome in a post-RYGB population.

METHODS

Randomized, double-blind, placebo-controlled trial of 20 postmenopausal women with history of RYGB a mean 5 years prior; a 2-month course of 20 g/day SCF or maltodextrin placebo was taken orally. The main outcome measure was between-group difference in absolute change in FCA (primary outcome) and was measured with a gold standard dual stable isotope method. Other measures included tolerability, adherence, serum calciotropic hormones and bone turnover markers, and fecal microbial composition via 16S rRNA gene sequencing.

RESULTS

Mean FCA ± SD at baseline was low at 5.5 ± 5.1%. Comparing SCF to placebo, there was no between-group difference in mean (95% CI) change in FCA (+3.4 [-6.7, +13.6]%), nor in calciotropic hormones or bone turnover markers. The SCF group had a wider variation in FCA change than placebo (SD 13.4% vs 7.0%). Those with greater change in microbial composition following SCF treatment had greater increase in FCA (r2 = 0.72, P = 0.05). SCF adherence was high, and gastrointestinal symptoms were similar between groups.

CONCLUSION

No between-group differences were observed in changes in FCA or calciotropic hormones, but wide CIs suggest a variable impact of SCF that may be due to the degree of gut microbiome alteration. Daily SCF consumption was well tolerated. Larger and longer-term studies are warranted.

Integration of the Human Gut Microbiome and Serum Metabolome Reveals Novel Biological Factors Involved in the Regulation of Bone Mineral Density

While the gut microbiome has been reported to play a role in bone metabolism, the individual species and underlying functional mechanisms have not yet been characterized. We conducted a systematic multi-omics analysis using paired metagenomic and untargeted serum metabolomic profiles from a large sample of 499 peri- and early post-menopausal women to identify the potential crosstalk between these biological factors which may be involved in the regulation of bone mineral density (BMD). Single omics association analyses identified 22 bacteria species and 17 serum metabolites for putative association with BMD. Among the identified bacteria, Bacteroidetes and Fusobacteria were negatively associated, while Firmicutes were positively associated. Several of the identified serum metabolites including 3-phenylpropanoic acid, mainly derived from dietary polyphenols, and glycolithocholic acid, a secondary bile acid, are metabolic byproducts of the microbiota. We further conducted a supervised integrative feature selection with respect to BMD and constructed the inter-omics partial correlation network. Although still requiring replication and validation in future studies, the findings from this exploratory analysis provide novel insights into the interrelationships between the gut microbiome and serum metabolome that may potentially play a role in skeletal remodeling processes.

Advances in pathogenesis and therapeutic strategies for osteoporosis

Osteoporosis, is the most common bone disorder worldwide characterized by low bone mineral density, leaving affected bones vulnerable to fracture. Bone homeostasis depends on the precise balance between bone resorption by osteoclasts and bone matrix formation by mesenchymal lineage osteoblasts, and involves a series of complex and highly regulated steps. Bone homeostasis will be disrupted when the speed of bone resorption is faster than bone formation. Based on various regulatory mechanisms of bone homeostasis, a series of drugs targeting osteoporosis have emerged in clinical practice, including bisphosphonates, selective estrogen receptor modulators, calcitonin, molecular-targeted drugs and so on. However, many drugs have major adverse effects or are unsuitable for long-term use. Therefore, it is very urgent to find more effective therapeutic drugs based on the new pathogenesis of osteoporosis. In this review, we summarize novel mechanisms involved in the pathological process of osteoporosis, including the roles of gut microbiome, autophagy, iron balance and cellular senescence. Based on the above pathological mechanism, we found promising drugs for osteoporosis treatment, such as: probiotics, alpha-ketoglutarate, senolytics and hydrogen sulfide. This new finding may provide an important basis for elucidating the complex pathological mechanisms of osteoporosis and provide promising drugs for clinical osteoporosis treatment.

Role of Dietary Supplements and Probiotics in Modulating Microbiota and Bone Health: The Gut-Bone Axis

Osteoporosis is characterized by an alteration of bone microstructure with a decreased bone mineral density, leading to the incidence of fragility fractures. Around 200 million people are affected by osteoporosis, representing a major health burden worldwide. Several factors are involved in the pathogenesis of osteoporosis. Today, altered intestinal homeostasis is being investigated as a potential additional risk factor for reduced bone health and, therefore, as a novel potential therapeutic target. The intestinal microflora influences osteoclasts’ activity by regulating the serum levels of IGF-1, while also acting on the intestinal absorption of calcium. It is therefore not surprising that gut dysbiosis impacts bone health. Microbiota alterations affect the OPG/RANKL pathway in osteoclasts, and are correlated with reduced bone strength and quality. In this context, it has been hypothesized that dietary supplements, prebiotics, and probiotics contribute to the intestinal microecological balance that is important for bone health. The aim of the present comprehensive review is to describe the state of the art on the role of dietary supplements and probiotics as therapeutic agents for bone health regulation and osteoporosis, through gut microbiota modulation.

Acidification of drinking water improvement tibia mass of broilers associated with the alterations in intestinal barrier and microbiota

Objective

Diet acidification supplementation is known to influence intestinal morphology, gut microbiota, and on phosphorus (P) utilization of broilers. Alterations in intestinal barrier and microbiota have been associated with systemic inflammation and thus regulating bone turnover. Hence the effect of acidifier addition to drinking water on tibia mass and the linkages between intestinal integrity and bone were studied.

Methods

One-d-old male broilers were randomly assigned to normal water (control) or continuous supply of acidified water (2% the blend of 2-hydroxy-4-methylthiobutyric acid, lactic, and phosphoric acid) group with 5 replicates of 10 chicks per replicate for 42 d.

Results

Acidification of drinking water improved the ash percentage and calcium content of tibia at 42 d. Broilers receiving acidified water had increased serum P concentration compared to control birds. The acidified group showed improved intestinal barrier, evidenced by increased wall thickness, villus height, the villus height to crypt depth ratio, and upregulated mucin-2 expression in ileum. Broilers receiving drinking water containing mixed organic acids had a higher proportion of Firmicutes and the ratio of Firmicutes and Bacteroidetes, as well as a lower population of Proteobacteria. Meanwhile, the addition of acidifier to drinking water resulted in declined ileal and serum proinflammatory factors level and increased immunoglobulin concentrations in serum. Concerning bone remodeling, acidifier addition was linked to a decrease in serum C-terminal cross-linked telopeptide of type I collagen and tartrate-resistant acid phosphatase reflecting bone resorption, whereas it did not apparently change serum alkaline phosphatase activity that is a bone formation marker.

Conclusion

Acidified drinking water increased tibia mineral deposition of broilers, which was probably linked with higher P utilization and decreased bone resorption through improved intestinal integrity and gut microbiota and through decreased systemic inflammation.

The rising dominance of microbiology: what to expect in the next 15 years?

What microbiology beholds after a decade and a half in the future requires a vision based on the facts and ongoing trends in research and technological advancements. While the latter, assisted by microbial dark matter, presents a greater potential of creating an upsurge in in-situ and ex-situ rapid microbial detection techniques, this anticipated change will also set forth a revolution in microbial cultivation and diversity analyses. The availability of a microbial genetic toolbox at the expanse will help complement the current understanding of the microbiome and assist in real-time monitoring of the dynamics for detecting the health status of the host with utmost precision. Alongside, in light of the emerging infectious diseases, antimicrobial resistance (AMR) and social demands for safer and better health care alternatives, microbiology laboratories are prospected to drift in terms of the volume and nature of research and outcomes. With today's microbiological lens, one can predict with certainty that in the years to come, microbes will play a significant role in therapeutic treatment and the designing of novel diagnostic techniques. Another area where the scope of microbial application seems to be promising is the use of novel probiotics as a method to offer health benefits whilst promoting metabolic outputs specific for microbiome replenishment. Nonetheless, the evolution of extraterrestrial microbes or the adaptation of earth microbes as extraterrestrial residents are also yet another prominent microbial event one may witness in the upcoming years. But like the two sides of the coin, there is also an urgent need to dampen the bloom of urbanization, overpopulation and global trade and adopting sustainable approaches to control the recurrence of epidemics and pandemics.

The gut microbiome is associated with bone turnover markers in postmenopausal women

OBJECTIVE

The association of the gut microbiome with bone turnover markers (BTMs) in postmenopausal women is poorly understood.

METHODS

Fecal samples were collected from 97 Chinese postmenopausal women, and the serum CTX and P1NP were determined. Individuals with serum CTX lower or higher than the median value were divided into LCTX and P1NP groups; and individuals with serum P1NP lower or higher than the median value were grouped into LP1NP and HP1NP groups. Microbiota profiles were determined by high-throughput 16S rRNA gene sequencing.

RESULTS

In postmenopausal women, only Faecalibacterium showed significant alteration in the HCTX group compared with the LCTX group (P=0.004, q=0.143). Linear discriminant analysis effect size (LEfSe) analysis revealed that Clostridiaceae (P=0.015, LDA=2.89), Faecalibacterium (P=0.017, LDA=4.60), Prevotella (P=0.040, LDA=3.61) and Clostridium (P=0.007, LDA=2.79) were abundant in the LCTX group, and Facklamia (P=0.044, LDA=3.10) was enriched in the HCTX group. Peptostreptococcaceae (P=0.048, LDA=2.83) and the SMB53 (P=0.028, LDA=2.05) genus were enriched in the LPINP group, and Veillonellaceae (P=0.025, LDA=4.43) and the S24_7 (P=0.023, LDA=3.08) family were enriched in the HPINP group. Six taxa correlated with BTMs in all subjects, including Clostridium (Clostridiaceae) that was negatively correlated with serum CTX amounts significantly (r=-0.34, P<0.001).

CONCLUSION

This study identified taxa-specific differences in the intestinal microflora associated with BTMs, notably CTX. These findings may help in uncovering the roles of gut microbiota on bone metabolism.

Effects of probiotics on bone mineral density and bone turnover: A systematic review

Probiotic supplements have been shown to improve bone health in animal models, although it remains uncertain whether these beneficial effects extend to humans. We undertook a systematic review of the literature to determine the effects of probiotic interventions on skeletal outcomes in postmenopausal women. MEDLINE, EMBASE, CENTRAL, and the Cochrane Database of Systematic Reviews were searched from inception to October 2020 for controlled trials comparing the effects of probiotic-containing supplements with placebo on bone mineral density (BMD) or bone turnover markers. Risk of bias was assessed using the Cochrane Risk of Bias 2 Tool. Of 338 records identified, six randomized, placebo-controlled trials (n = 632) were eligible for inclusion. All studies assessed postmenopausal women for durations of 6-12 months; three were considered to be at high risk of bias. Four studies examined Lactobacillus-containing probiotics, one assessed a proprietary blend of lactic acid bacteria, and one evaluated Bacillus subtilis. Effects of probiotic interventions on BMD were inconsistent, with the majority of studies demonstrating no benefit at the spine or hip. Probiotic effects on bone turnover markers were similarly heterogeneous. High quality studies are needed to determine whether probiotic interventions have a role in maintaining bone health in humans.

25-hydroxycholecalciferol reverses heat induced alterations in bone quality in finisher broilers associated with effects on intestinal integrity and inflammation

BACKGROUND

Alterations in ambient temperature have been associated with multiple detrimental effects on broilers such as intestinal barrier disruption and dysbiosis resulting in systemic inflammation. Inflammation and 25-hydroxycholecalciferol (25-OH-D₃) have shown to play a negative and positive role, respectively, in the regulation of bone mass. Hence the potential of 25-OH-D₃ in alleviating heat induced bone alterations and its mechanisms was studied.

RESULTS

Heat stress (HS) directly induced a decrease in tibia material properties and bone mass, as demonstrated by lower mineral content, and HS caused a notable increase in intestinal permeability. Treatment with dietary 25-OH-D₃ reversed the HS-induced bone loss and barrier leak. Broilers suffering from HS exhibited dysbiosis and increased expression of inflammatory cytokines in the ileum and bone marrow, as well as increased osteoclast number and activity. The changes were prevented by dietary 25-OH-D₃ administration. Specifically, dietary 25-OH-D₃ addition decreased abundance of B- and T-cells in blood, and the expression of inflammatory cytokines, especially TNF-α, in both the ileum and bone marrow, but did not alter the diversity and population or composition of major bacterial phyla. With regard to bone remodeling, dietary 25-OH-D₃ supplementation was linked to a decrease in serum C-terminal cross-linked telopeptide of type I collagen reflecting bone resorption and a concomitant decrement in osteoclast-specific marker genes expression (e.g. cathepsin K), whereas it did not apparently change serum bone formation markers during HS.

CONCLUSIONS

These data underscore the damage of HS to intestinal integrity and bone health, as well as that dietary 25-OH-D₃ supplementation was identified as a potential therapy for preventing these adverse effects.

Crosstalk between immune cells and bone cells or chondrocytes

The term "osteoimmunology" was coined to denote the bridge between the immune system and the skeletal system. Osteoimmunology is interdisciplinary, and a full understanding and development of this "bridge" will provide an in-depth understanding of the switch between body health and disease development. B lymphocytes can promote the maturation and differentiation of osteoclasts, and osteoclasts have a negative feedback effect on B lymphocytes. Different subtypes of T lymphocytes regulate osteoclasts in different directions. T lymphocytes have a two-way regulatory effect on osteoblasts, while B lymphocytes have minimal regulatory effects on osteoblasts. In contrast, osteoblasts can promote the differentiation and maturation of T lymphocytes and B lymphocytes. Different immune cells have different effects on chondrocytes; some cooperate with each other, while some antagonize each other. In a healthy adult body, bone resorption and bone formation are in a dynamic balance under the action of multiple mechanisms. In this review, we summarize the interactions and key signaling molecular mechanisms between each type of cell in the immune system and the skeletal system.