Lactobacillus acidophilus inhibits bone loss and increases bone heterogeneity in osteoporotic mice via modulating Treg-Th17 cell balance

The Potential Value of Probiotics after Dental Implant Placement

Dental implantation is currently the optimal solution for tooth loss. However, the health and stability of dental implants have emerged as global public health concerns. Dental implant placement, healing of the surgical site, osseointegration, stability of bone tissues, and prevention of peri-implant diseases are challenges faced in achieving the long-term health and stability of implants. These have been ongoing concerns in the field of oral implantation. Probiotics, as beneficial microorganisms, play a significant role in the body by inhibiting pathogens, promoting bone tissue homeostasis, and facilitating tissue regeneration, modulating immune-inflammatory levels. This review explores the potential of probiotics in addressing post-implantation challenges. We summarize the existing research regarding the importance of probiotics in managing dental implant health and advocate for further research into their potential applications.

Meta-Analysis Reveals Compositional and Functional Microbial Changes Associated with Osteoporosis

Over the past decade, the role of the gut microbiota in many disease states has gained a great deal of attention. Mounting evidence from case-control and observational studies has linked changes in the gut microbiota to the pathophysiology of osteoporosis (OP). Nonetheless, the results of these studies contain discrepancies, leaving the literature without a consensus on osteoporosis-associated microbial signatures. Here, we conducted a comprehensive meta-analysis combining and reexamining five publicly available 16S rRNA partial sequence data sets to identify gut bacteria consistently associated with osteoporosis across different cohorts. After adjusting for the batch effect associated with technical variation and heterogeneity of studies, we observed a significant shift in the microbiota composition in the osteoporosis group. An increase in the relative abundance of opportunistic pathogens Clostridium sensu stricto, Bacteroides, and Intestinibacter was observed in the OP group. Moreover, short-chain-fatty-acid (SCFA) producers, including members of the genera Collinsella, Megasphaera, Agathobaculum, Mediterraneibacter, Clostridium XIV, and Dorea, were depleted in the OP group relative to the healthy control (HC) group. Lactic acid-producing bacteria, including Limosilactobacillus, were significantly increased in the OP group. The random forest algorithm further confirmed that these bacteria differentiate the two groups. Furthermore, functional prediction revealed depletion of the SCFA biosynthesis pathway (glycolysis, tricarboxylic acid [TCA] cycle, and Wood-Ljungdahl pathway) and amino acid biosynthesis pathway (methionine, histidine, and arginine) in the OP group relative to the HC group. This study uncovered OP-associated compositional and functional microbial alterations, providing robust insight into OP pathogenesis and aiding the possible development of a therapeutic intervention to manage the disease. IMPORTANCE Osteoporosis is the most common metabolic bone disease associated with aging. Mounting evidence has linked changes in the gut microbiota to the pathophysiology of osteoporosis. However, which microbes are associated with dysbiosis and their impact on bone density and inflammation remain largely unknown due to inconsistent results in the literature. Here, we present a meta-analysis with a standard workflow, robust statistical approaches, and machine learning algorithms to identify notable microbial compositional changes influencing osteoporosis.

Modulation of bone remodeling by the gut microbiota: a new therapy for osteoporosis

The gut microbiota (GM) plays a crucial role in maintaining the overall health and well-being of the host. Recent studies have demonstrated that the GM may significantly influence bone metabolism and degenerative skeletal diseases, such as osteoporosis (OP). Interventions targeting GM modification, including probiotics or antibiotics, have been found to affect bone remodeling. This review provides a comprehensive summary of recent research on the role of GM in regulating bone remodeling and seeks to elucidate the regulatory mechanism from various perspectives, such as the interaction with the immune system, interplay with estrogen or parathyroid hormone (PTH), the impact of GM metabolites, and the effect of extracellular vesicles (EVs). Moreover, this review explores the potential of probiotics as a therapeutic approach for OP. The insights presented may contribute to the development of innovative GM-targeted therapies for OP.

Lactobacillus acidophilus supernatant alleviates osteoporosis by upregulating colonic SERT expression

Aims: To investigate the involvement of serotonin transporter (SERT) in colonic epithelial cells in the anti-osteoporosis role of Lactobacillus acidophilus (LA) supernatant (LAS). Methods: The abundance of fecal LA and bone mineral density (BMD) in patients with osteoporosis (OP) or severe osteoporosis were assessed. The protective role of LA in osteoporosis and the expression of SERT and relative signaling were evaluated. Results: Abundance of fecal LA was decreased in patients with severe OP and was positively correlated with BMD. Supplementing LAS to mice alleviated senile osteoporosis. In vitro, NOD2/RIP2/NF-κB signaling was inhibited by LAS due to increased SERT expression. Conclusion: LAS alleviates OP in mice by producing protective metabolites and upregulating SERT expression and represents a promising therapeutic agent.

Isoflavones and probiotics effect on bone calcium and bone cells in rats

Isoflavones and probiotics have shown the therapeutic potential to alter calcium absorption and bone cell metabolism. This study sought to ascertain the effect of isoflavones and probiotics on calcium status and bone health in healthy female rats. Forty-eight adult female Wistar rats were grouped and fed: a standard diet (control); and standard diets with tempeh; soy; daidzein and genistein; Lactobacillus acidophilus; and a combination of daidzein, genistein, and L. acidophilus. The biochemical serum parameters, such as alanine transaminase, aspartate transaminase, glucose, and triacylglycerol concentrations, were measured, and calcium contents in tissues were determined. After staining the bone with hematoxylin and eosin, the number of osteoblasts, osteocytes, and the percentage of bone marrow adipocytes were counted. Compared with the control group, the soy group showed a significantly lower triacylglycerol concentration. The L. acidophilus group considerably increased the calcium content in the femoral bone. The daidzein and genistein, L. acidophilus, and a combination of daidzein, genistein, and L. acidophilus groups showed significantly lower calcium contents in the heart and kidneys. The daidzein and genistein group significantly enhanced the number of osteoblasts and osteocytes. A substantial inverse correlation was observed between calcium contents in kidneys and osteoblasts. In conclusion, the combination of daidzein, genistein, and L. acidophilus may improve bone calcium concentrations and bone cells. However, no synergistic effect between isoflavones and probiotics was detected in this study.

Fine-tuning osteoclastogenesis: An insight into the cellular and molecular regulation of osteoclastogenesis

Osteoclasts, the bone-resorbing cells, are essential for the bone remodeling process and are involved in the pathophysiology of several bone-related diseases. The extensive corpus of in vitro research and crucial mouse model studies in the 1990s demonstrated the key roles of monocyte/macrophage colony-stimulating factor, receptor activator of nuclear factor kappa B ligand (RANKL) and integrin αvβ3 in osteoclast biology. Our knowledge of the molecular mechanisms by which these variables control osteoclast differentiation and function has significantly advanced in the first decade of this century. Recent developments have revealed a number of novel insights into the fundamental mechanisms governing the differentiation and functional activity of osteoclasts; however, these mechanisms have not yet been adequately documented. Thus, in the present review, we discuss various regulatory factors including local and hormonal factors, innate as well as adaptive immune cells, noncoding RNAs (ncRNAs), etc., in the molecular regulation of the intricate and tightly regulated process of osteoclastogenesis. ncRNAs have a critical role as epigenetic controllers of osteoclast physiologic activities, including differentiation and bone resorption. The primary ncRNAs, which include micro-RNAs, circular RNAs, and long noncoding RNAs, form a complex network that affects gene transcription activities associated with osteoclast biological activity. Greater knowledge of the involvement of ncRNAs in osteoclast biological activities will contribute to the treatment and management of several skeletal diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, etc. Moreover, we further outline potential therapies targeting these regulatory pathways of osteoclastogenesis in distinct bone pathologies.

Recent advances of osteoimmunology research in rheumatoid arthritis: From single-cell omics approach

ABSTRACT

Cellular immune responses as well as generalized and periarticular bone loss are the key pathogenic features of rheumatoid arthritis (RA). Under the pathological conditions of RA, dysregulated inflammation and immune processes tightly interact with skeletal system, resulting in pathological bone damage via inhibition of bone formation or induction of bone resorption. Single-cell omics technologies are revolutionary tools in the field of modern biological research.They enable the display of the state and function of cells in various environments from a single-cell resolution, thus making it conducive to identify the dysregulated molecular mechanisms of bone destruction in RA as well as the discovery of potential therapeutic targets and biomarkers. Here, we summarize the latest findings of single-cell omics technologies in osteoimmunology research in RA. These results suggest that single-cell omics have made significant contributions to transcriptomics and dynamics of specific cells involved in bone remodeling, providing a new direction for our understanding of cellular heterogeneity in the study of osteoimmunology in RA.

Impact of T helper cells on bone metabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE), an autoimmune disease affecting multiple organs and tissues, is often complicated by musculoskeletal diseases. T helper cells (Th) play an important role in mediating lupus. With the rise of osteoimmunology, more studies have shown shared molecules and interactions between the immune system and bones. Th cells are vital in the regulation of bone metabolism by directly or indirectly regulating bone health by secreting various cytokines. Therefore, by describing the regulation of Th cells (including Th1, Th2, Th9, Th17, Th22, regulatory T cells (Treg), and follicular T helper cells (Tfh) in bone metabolism in SLE, this paper offers certain theoretical support for abnormal bone metabolism in SLE and provides new prospects for future drug development.

Identifying microbial signatures for patients with postmenopausal osteoporosis using gut microbiota analyses and feature selection approaches

Osteoporosis (OP) is a metabolic bone disorder characterized by low bone mass and deterioration of micro-architectural bone tissue. The most common type of OP is postmenopausal osteoporosis (PMOP), with fragility fractures becoming a global burden for women. Recently, the gut microbiota has been connected to bone metabolism. The aim of this study was to characterize the gut microbiota signatures in PMOP patients and controls. Fecal samples from 21 PMOP patients and 37 controls were collected and analyzed using amplicon sequencing of the V3-V4 regions of the 16S rRNA gene. The bone mineral density (BMD) measurement and laboratory biochemical test were performed on all participants. Two feature selection algorithms, maximal information coefficient (MIC) and XGBoost, were employed to identify the PMOP-related microbial features. Results showed that the composition of gut microbiota changed in PMOP patients, and microbial abundances were more correlated with total hip BMD/T-score than lumbar spine BMD/T-score. Using the MIC and XGBoost methods, we identified a set of PMOP-related microbes; a logistic regression model revealed that two microbial markers (Fusobacteria and Lactobacillaceae) had significant abilities in disease classification between the PMOP and control groups. Taken together, the findings of this study provide new insights into the etiology of OP/PMOP, as well as modulating gut microbiota as a therapeutic target in the diseases. We also highlight the application of feature selection approaches in biological data mining and data analysis, which may improve the research in medical and life sciences.

Valgus-varus deformity induced abnormal tissue metabolism, inflammatory damage and apoptosis in broilers

1. This study explored the tissue metabolic status and the relationship with inflammation in valgus-valgus deformity (VVD) broilers with increasing age.2. Tissue and blood from VVD and healthy broilers were collected at two, four and five weeks old. A fully automated biochemical analyser, real-time PCR, HE staining and enzyme-linked immunosorbent assay were used to detect tissue metabolic indexes, mRNA levels of inflammation and apoptosis cytokines in immune organs, histological changes and serum inflammation and immune-related protein contents in VVD broilers.3. The results showed that VVD increased the levels of total protein, albumin, alanine aminotransferase at five weeks of age, aspartate aminotransferase, urea and creatine kinase in blood at two weeks of age. It upregulated the gene expression of inflammatory factors IL-1β, IL-6, IL-8, TNF-α, NF-κB and TGF-β and apoptotic factors FAS, Bcl-2, caspase-3 and 9 in immune organs; increased levels of serum proteins TNF-α, IL-1β and IL-6 and decreased levels of serum immunoglobulins IgY and CD3⁺.4. In addition, with increasing age, IL-10 gene expression gradually increased in the BF and decreased in the spleen.5. In conclusion, VVD broilers have disorders of liver and kidney metabolism, inflammation and apoptosis of immune organs and increased levels of serum inflammatory factor proteins.

Randomized clinical trial to test the safety and tolerability of SBD111, an optimized synbiotic medical food combination designed for the dietary management of the metabolic processes underlying osteopenia and osteoporosis

To determine the effect of a twice daily administration of SBD111 on safety and tolerability in healthy adults in a randomized, placebo-controlled trial over 28-days. Participants were randomized to either SBD111 (n=15) or placebo (n=17). The outcomes were the number, frequency, and severity of Gastrointestinal (GI) symptoms and the number and severity of adverse events (AEs) over 28-days. Stool samples were collected and analyzed at baseline, after 28- and 56-days. Groups were compared (P< 0.05) using an intention-to-treat approach. The two groups were similar at baseline. After 28-days, the presence of GI symptoms tended to be higher with SBD111 use vs placebo (P=0.08) but the total number, frequency/severity of GI symptoms did not significantly differ. The number of AEs possibly related to the study were higher with SBD111 use vs placebo (P=0.05), there were no significant differences in the mean number/severity of AEs. The majority of reported AEs were mild, some were moderate, but none were severe. There were no significant differences in alpha diversity indices between the two groups at baseline or follow-up. SBD111 strains were identified in stool, enriched metabolic pathways for menaquinone (vitamin K2) production at 28-days, and were not detected at 56-days. The relatively low frequency and mild severity of GI symptoms and AEs suggests that SBD111 at the level tested is safe for human consumption.

Lactobacillus acidophilus (LA) Fermenting Astragalus Polysaccharides (APS) Improves Calcium Absorption and Osteoporosis by Altering Gut Microbiota

Lactobacillus acidophilus (LA) and Astragalus polysaccharides (APS) have each been shown to have anti-osteoporotic activity, and the aim of this study was to further investigate whether the LA fermenting APS was more effective in improving calcium absorption and osteoporosis than the unfermented mixed solution (MS). We found that the fermentation solution (FS) intervention improved the calcium absorption, BMD, and bone microarchitecture in osteoporotic rats and resulted in better inhibition of osteoclast differentiation markers ACP-5 and pro-inflammatory cytokines TNF-α and IL-6 and promotion of osteoblast differentiation marker OCN. This better performance may be due to the improved restoration of the relative abundance of specific bacteria associated with improved calcium absorption and osteoporosis such as Lactobacillus, Allobaculum, and UCG-005. Several key metabolites, including indicaxanthin, chlorogenic acid, and 3-hydroxymelatonin, may also be the key to the better improvement. In conclusion, the LA fermenting APS can better improve calcium absorption and osteoporosis by increasing active metabolites and altering gut microbiota. This finding should become a solid foundation for the development of LA fermenting APS in functional foods.

Cissus quadrangularis (Hadjod) Inhibits RANKL-Induced Osteoclastogenesis and Augments Bone Health in an Estrogen-Deficient Preclinical Model of Osteoporosis Via Modulating the Host Osteoimmune System

Osteoporosis is a systemic skeletal disease characterised by low bone mineral density (BMD), degeneration of bone micro-architecture, and impaired bone strength. Cissus quadrangularis (CQ), popularly known as Hadjod (bone setter) in Hindi, is a traditional medicinal herb exhibiting osteoprotective potential in various bone diseases, especially osteoporosis and fractures. However, the cellular mechanisms underpinning its direct effect on bone health through altering the host immune system have never been elucidated. In the present study, we interrogated the osteoprotective and immunoporotic (the osteoprotective potential of CQ via modulating the host immune system) potential of CQ in preventing inflammatory bone loss under oestrogen-deficient conditions. The current study outlines the CQ's osteoprotective potential under both ex vivo and in vivo (ovariectomized) conditions. Our ex vivo data demonstrated that, in a dose-dependent manner CQ, suppresses the RANKL-induced osteoclastogenesis (p < 0.001) as well as inhibiting the osteoclast functional activity (p < 0.001) in mouse bone marrow cells (BMCs). Our in vivo µ-CT and flow cytometry data further showed that CQ administration improves bone health and preserves bone micro-architecture by markedly raising the proportion of anti-osteoclastogenic immune cells, such as Th1 (p < 0.05), Th2 (p < 0.05), Tregs (p < 0.05), and Bregs (p < 0.01), while concurrently lowering the osteoclastogenic Th17 cells in bone marrow, mesenteric lymph nodes, Peyer's patches, and spleen in comparison to the control group. Serum cytokine analysis further supported the osteoprotective and immunoporotic potential of CQ, showing a significant increase in the levels of anti-osteoclastogenic cytokines (p < 0.05) (IFN-γ, IL-4, and IL-10) and a concurrent decrease in the levels of osteoclastogenic cytokines (p < 0.05) (TNF-α, IL-6, and IL-17). In conclusion, our data for the first time delineates the novel cellular and immunological mechanism of the osteoprotective potential of CQ under postmenopausal osteoporotic conditions.

Transplantation of gut microbiota from old mice into young healthy mice reduces lean mass but not bone mass

Aging is associated with low bone and lean mass as well as alterations in the gut microbiota (GM). In this study, we determined whether the reduced bone mass and relative lean mass observed in old mice could be transferred to healthy young mice by GM transplantation (GMT). GM from old (21-month-old) and young adult (5-month-old) donors was used to colonize germ-free (GF) mice in three separate studies involving still growing 5- or 11-week-old recipients and 17-week-old recipients with minimal bone growth. The GM of the recipient mice was similar to that of the donors, demonstrating successful GMT. GM from old mice did not have statistically significant effects on bone mass or bone strength, but significantly reduced the lean mass percentage of still growing recipient mice when compared with recipients of GM from young adult mice. The levels of propionate in the cecum of mice receiving old donor GM were significantly lower than those in mice receiving young adult donor GM. Bacteroides ovatus was enriched in the microbiota of recipient mice harboring GM from young adult donors. The presence of B. ovatus was not only significantly associated with high lean mass percentage in mice, but also with lean mass adjusted for fat mass in the large human HUNT cohort. In conclusion, GM from old mice reduces lean mass percentage but not bone mass in young, healthy, still growing recipient mice. Future studies are warranted to determine whether GM from young mice improves the musculoskeletal phenotype of frail elderly recipient mice.

Lactobacillus rhamnosus GG ameliorates osteoporosis in ovariectomized rats by regulating the Th17/Treg balance and gut microbiota structure

BACKGROUND

With increasing knowledge about the gut - bone axis, more studies for treatments based on the regulation of postmenopausal osteoporosis by gut microbes are being conducted. Based on our previous work, this study was conducted to further investigate the therapeutic effects of Lactobacillus rhamnosus GG (LGG) on ovariectomized (OVX) model rats and the immunological and microecological mechanisms involved.

RESULTS

We found a protective effect of LGG treatment in OVX rats through changes in bone microarchitecture, bone biomechanics, and CTX-I, PINP, Ca, and RANKL expression levels. LGG was more advantageous in promoting osteogenesis, which may be responsible for the alleviation of osteoporosis. Th17 cells were imbalanced with Treg cells in mediastinal lymph nodes and bone marrow, with RORγt and FOXP3 expression following a similar trend. TNF-α and IL-17 expression in colon and bone marrow increased, while TGF-β and IL-10 expression decreased; however, LGG treatment modulated these changes and improved the Th17/Treg balance significantly. Regarding the intestinal barrier, we found that LGG treatment ameliorated estrogen deficiency-induced inflammation and mucosal damage and increased the expression of GLP-2 R and tight junction proteins. Importantly, 16S rRNA sequencing showed a significant increase in the Firmicutes/Bacteroidetes ratio during estrogen deficiency. Dominant intestinal flora showed significant differences in composition; LGG treatment regulated the various genera that were imbalanced in OVX, along with modifying those that did not change significantly in other groups with respect to the intestinal barrier, inflammation development, and bile acid metabolism.

CONCLUSIONS

Overall, LGG ameliorated estrogen deficiency-induced osteoporosis by regulating the gut microbiome and intestinal barrier and stimulating Th17/Treg balance in gut and bone.

The potential mechanism of the microbiota-gut-bone axis in osteoporosis: a review

Osteoporosis is the prevalent metabolic bone disease characterized by a decrease in bone quantity and/or quality and an increase in skeletal fragility, which increases susceptibility to fractures. Osteoporotic fractures severely affect the patients' quality of life and mortality. A plethora of evidences have suggested that the alterations in gut microbiome are associated with the changes in bone mass and microstructure. We summarized pre-clinical and clinical studies to elucidate the underlying mechanism of gut microbiota in osteoporosis. Probiotics, prebiotics, and traditional Chinese medicine may reverse the gut microbiota dysbiosis and consequently improve bone metabolism. However, the causality of gut microbiota on bone metabolism need to be investigated more in depth. In the present review, we focused on the potential mechanism of the microbiota-gut-bone axis and the positive therapeutic effect of probiotics, prebiotics, and traditional Chinese medicine on osteoporosis. Overall, the current scientific literatures support that the gut microbiota may be a novel therapeutic target in treatment of osteoporosis and fracture prevention.

Lactic Acid Bacteria: A Promising Tool for Menopausal Health Management in Women

Menopause is a period during which women undergo dramatic hormonal changes. These changes lead to physical and mental discomfort, are greatly afflictive, and critically affect women's lives. However, the current safe and effective management measures for women undergoing menopause are insufficient. Several probiotic functions of lactic acid bacteria (LAB) have been recognized, including alleviation of lactose intolerance, protection of digestive tract health, activation of the immune system, protection against infections, improvement of nutrient uptake, and improvement of the microbiota. In this review, we highlight the currently available knowledge of the potential protective effects of LAB on preventing or mitigating menopausal symptoms, particularly in terms of maintaining balance in the vaginal microbiota, reducing bone loss, and regulating the nervous system and lipid metabolism. Given the increasing number of women entering menopause and the emphasis on the management of menopausal symptoms, LAB are likely to soon become an indispensable part of clinical/daily care for menopausal women. Herein, we do not intend to provide a comprehensive analysis of each menopausal disorder or to specifically judge the reliability and safety of complementary therapies; rather, we aim to highlight the potential roles of LAB in individualized treatment strategies for the clinical management of menopause.

The ameliorative role of specific probiotic combinations on bone loss in the ovariectomized rat model

Background

Osteoporosis, a skeletal disease described by impaired bone strength, cause an increased risk of fractures. We aimed in this study to clarify which particular wise combination of probiotics has the most beneficial effect in the rat model of osteoporosis.

Methods

Sixty-three mature female Sprague Dawley rats (12–14 weeks old, weight 200 ± 20 g) were ovariectomized and then divided into nine random groups, each group consisting of 7 rats. Lactic acid bacteria were isolated from traditional fermented yogurt on the northern coast of the Persian Gulf. Seven combinations of probiotics, each containing three probiotic strains, were designed and administered (1 × 10 9 CFU / ml/strain daily along with their water) to treat ovariectomized rats. The period from ovariectomy to eutanásia was 3 months. For evaluating femur, spine, and tibia, bone mineral density (BMD), and bone mineral content (BMC), Dual-energy X-ray absorptiometry (DEXA) scans were performed. Also, effect of probiotic combinations was assessed on biochemical markers including vitamin D, calcium, phosphorus, and alkaline phosphatase in serum.

Results

Combination NO 4, containing L. acidophilus, B. longum, and L. reuteri, is the most influential group on global, spine, and femur BMD. Combination NO 3, containing L. acidophilus, L. casei, and L. reuteri, also significantly affects the BMD of the tibia among the treatment group. We found that the combination NO 4 had the most significant ameliorative effect on global BMC. Also, combination NO 1 (comprising L. acidophilus, L. casei, and B. longum), NO 6 (containing L. casei, B. longum, and Bacillus coagulans), NO 7 (containing L. casei, L. reuteri, and B. longum), and NO 4 had the most considerable raising effect on spine BMC. In addition, the serum calcium and Vitamin D concentration in the groups NO 4, 6, and 7 were significantly higher than in OVX groups, whereas the alkaline phosphatase concentration was considerably reduced in these groups.

Conclusion

Among nine effective probiotics, a combination containing L. acidophilus, B. longum, and L. reuteri is the most influential group in ovariectomized osteoporotic rat.

Long-term implications of COVID-19 on bone health: pathophysiology and therapeutics

BACKGROUND

SARS-CoV-2 is a highly infectious respiratory virus associated with coronavirus disease (COVID-19). Discoveries in the field revealed that inflammatory conditions exert a negative impact on bone metabolism; however, only limited studies reported the consequences of SARS-CoV-2 infection on skeletal homeostasis. Inflammatory immune cells (T helper-Th17 cells and macrophages) and their signature cytokines such as interleukin (IL)-6, IL-17, and tumor necrosis factor-alpha (TNF-α) are the major contributors to the cytokine storm observed in COVID-19 disease. Our group along with others has proven that an enhanced population of both inflammatory innate (Dendritic cells-DCs, macrophages, etc.) and adaptive (Th1, Th17, etc.) immune cells, along with their signature cytokines (IL-17, TNF-α, IFN-γ, IL-6, etc.), are associated with various inflammatory bone loss conditions. Moreover, several pieces of evidence suggest that SARS-CoV-2 infects various organs of the body via angiotensin-converting enzyme 2 (ACE2) receptors including bone cells (osteoblasts-OBs and osteoclasts-OCs). This evidence thus clearly highlights both the direct and indirect impact of SARS-CoV-2 on the physiological bone remodeling process. Moreover, data from the previous SARS-CoV outbreak in 2002-2004 revealed the long-term negative impact (decreased bone mineral density-BMDs) of these infections on bone health.

METHODOLOGY

We used the keywords "immunopathogenesis of SARS-CoV-2," "SARS-CoV-2 and bone cells," "factors influencing bone health and COVID-19," "GUT microbiota," and "COVID-19 and Bone health" to integrate the topics for making this review article by searching the following electronic databases: PubMed, Google Scholar, and Scopus.

CONCLUSION

Current evidence and reports indicate the direct relation between SARS-CoV-2 infection and bone health and thus warrant future research in this field. It would be imperative to assess the post-COVID-19 fracture risk of SARS-CoV-2-infected individuals by simultaneously monitoring them for bone metabolism/biochemical markers. Importantly, several emerging research suggest that dysbiosis of the gut microbiota-GM (established role in inflammatory bone loss conditions) is further involved in the severity of COVID-19 disease. In the present review, we thus also highlight the importance of dietary interventions including probiotics (modulating dysbiotic GM) as an adjunct therapeutic alternative in the treatment and management of long-term consequences of COVID-19 on bone health.

Effect of Administration of Azithromycin and/or Probiotic Bacteria on Bones of Estrogen-Deficient Rats

The gut microbiota plays an important role in maintaining homeostasis, including that of the skeletal system. Antibiotics may affect the skeletal system directly or indirectly by influencing the microbiota. Probiotic bacteria have been reported to favorably affect bones in conditions of estrogen deficiency. The aim of this study was to investigate the effects of azithromycin (AZM) administered alone or with probiotic bacteria (Lactobacillus rhamnosus; LR) on bones in estrogen-deficient rats. The experiments were carried out on mature rats divided into five groups: non-ovariectomized (NOVX) control rats, ovariectomized (OVX) control rats, and OVX rats treated with: LR, AZM, or AZM with LR. The drugs were administered for 4 weeks. Serum biochemical parameters, bone mineralization, histomorphometric parameters, and mechanical properties were examined. Estrogen deficiency increased bone turnover and worsened cancellous bone microarchitecture and mechanical properties. The administration of LR or AZM slightly favorably affected some skeletal parameters of estrogen-deficient rats. The administration of AZM with LR did not lead to the addition of the effects observed for the separate treatments, indicating that the effects could be microbiota-mediated.

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.

Crosstalk between the gut microbiota and postmenopausal osteoporosis: Mechanisms and applications

Postmenopausal osteoporosis (PMO) results from a reduction in bone mass and microarchitectural deterioration in bone tissue due to estrogen deficiency, which may increase the incidence of fragility fractures. The number of people suffering from PMO has increased over the years because of the rapidly aging population worldwide. However, several pharmacological agents for the treatment of PMO have many safety risks and impose a heavy financial burden to patients and society. In recent years, the "gut-bone" axis has been proposed as a new approach in the prevention and treatment of PMO. This paper reviews the relationship between the gut microbiota and PMO, which mainly includes the underlying mechanisms between hormones, immunity, nutrient metabolism, metabolites of the gut microbiota and intestinal permeability, and explores the possible role of the gut microbiota in these processes. Finally, we discuss the therapeutic effects of diet, prebiotics, probiotics, and fecal microbiota transplantation on the gut microbiota.

Bifidobacterium longum Ameliorates Ovariectomy-Induced Bone Loss via Enhancing Anti-Osteoclastogenic and Immunomodulatory Potential of Regulatory B Cells (Bregs)

Discoveries in the last few years have emphasized the existence of an enormous breadth of communication between osteo-immune systems. These discoveries fuel novel approaches for the treatment of several bone pathologies including osteoporosis. Bifidobacterium longum (BL) is a preferred probiotic of choice due to its varied immunomodulatory potential in alleviating various inflammatory diseases. Here, we evaluate the effect of BL in an ovariectomy (ovx)-induced post-menopausal osteoporotic mouse model. Our in vitro findings reveal that BL suppresses the differentiation and functional activity of RANKL-induced osteoclastogenesis in both mouse bone marrow cells and human PBMCs. Strikingly, BL-induced Bregs were found to be significantly more efficient in suppressing osteoclastogenesis and modulating Treg-Th17 cell balance with respect to control Bregs in vitro. Our in vivo µCT and bone mechanical strength data further confirm that BL supplementation significantly enhanced bone mass and bone strength, along with improving the bone microarchitecture in ovx mice. Remarkably, alterations in frequencies of CD19+CD1dhiCD5+IL-10+ Bregs, CD4+Foxp3+IL-10+ Tregs, and CD4+Rorγt+IL-17+ Th17 cells in distinct lymphoid organs along with serum-cytokine data (enhanced anti-osteoclastogenic cytokines IFN-γ and IL-10 and reduced osteoclastogenic-cytokines IL-6, IL-17, and TNF-α) strongly support the immunomodulatory potential of BL. Altogether, our findings establish a novel osteo-protective and immunomodulatory potential of BL in augmenting bone health under osteoporotic conditions.

Development of a synbiotic that protects against ovariectomy-induced trabecular bone loss

The gut microbiome has the capacity to regulate bone mass. The aim of this study was to develop a nutritional synbiotic dietary assemblage at an optimal dose to maintain bone mass in ovariectomized (Ovx) mice. We performed genomic analyses and in vitro experiments in a large collection of bacterial and fungal strains (>4,000) derived from fresh fruit and vegetables to identify candidates with the synergistic capacity to produce bone-protective short-chain fatty acids (SCFA) and vitamin K2. The candidate SBD111-A, composed of Lactiplantibacillus plantarum, Levilactobacillus brevis, Leuconostoc mesenteroides, Pseudomonas fluorescens, and Pichia kudriavzevii together with prebiotic dietary fibers, produced high levels of SCFA in vitro and protected against Ovx-induced trabecular bone loss in a dose-dependent manner in mice. Metagenomic sequencing revealed that SBD111-A changed the taxonomic composition and enriched specific pathways for synthesis of bone-protective SCFA, vitamin K2, and branched-chain amino acids in the gut microbiome.NEW & NOTEWORTHY We performed genomic analyses and in vitro experiments in a collection of bacterial and fungal strains. We identified a combination (SBD111-A) that produced high levels of SCFA in vitro and protected against ovariectomy-induced bone loss in a dose-dependent manner in mice. Metagenomic sequencing revealed that SBD111-A changed the taxonomic composition and function of the gut microbiome and enriched pathways for synthesis of bone-protective SCFA, vitamin K2, and branched-chain amino acids.

The regulative effect and repercussion of probiotics and prebiotics on osteoporosis: involvement of brain-gut-bone axis

Osteoporosis (OP) is a systemic disease characterized by decreased bone mass and degeneration of bone microstructure. In recent years, more and more researches have focused on the close relationship between gut microbiota (GM) and the occurrence and progression of OP, and the regulation of probiotics and prebiotics on bone metabolism has gradually become a research hotspot. Based on the influence of brain-gut-bone axis on bone metabolism, this review expounds the potential mechanisms of probiotics and prebiotics on OP from next perspectives: regulation of intestinal metabolites, regulation of intestinal epithelial barrier function, involvement of neuromodulation, involvement of immune regulation and involvement of endocrine regulation, so as to provide a novel and promising idea for the prevention and treatment of OP in the future.

The Rising Era of “Immunoporosis”: Role of Immune System in the Pathophysiology of Osteoporosis

Discoveries in the last few years have emphasized the existence of an enormous breadth of communication between bone and the immune system in maintaining skeletal homeostasis. Originally, the discovery of various factors was assigned to the immune system viz. interleukin (IL)-6, IL-10, IL-17, tumor necrosis factor (TNF)-α, receptor activator of nuclear factor kappa B ligand (RANKL), nuclear factor of activated T cells (NFATc1), etc., but now these factors have also been shown to have a significant impact on osteoblasts (OBs) and osteoclasts (OCs) biology. These discoveries led to an alteration in the approach for the treatment of several bone pathologies including osteoporosis. Osteoporosis is an inflammatory bone anomaly affecting more than 500 million people globally. In 2018, to highlight the importance of the immune system in the pathophysiology of osteoporosis, our group coined the term “immunoporosis”. In the present review, we exhaustively revisit the characteristics, mechanism of action, and function of both innate and adaptive immune cells with the goal of understanding the potential of immune cells in osteoporosis. We also highlight the Immunoporotic role of gut microbiota (GM) for the treatment and management of osteoporosis. Importantly, we further discuss whether an immune cell-based strategy to treat and manage osteoporosis is feasible and relevant in clinical settings.

FK506 and Lactobacillus acidophilus ameliorate acute graft-versus-host disease by modulating the T helper 17/regulatory T-cell balance

Background

Graft-versus-host disease (GvHD) is a critical complication after allogeneic hematopoietic stem cell transplantation (HSCT). The immunosuppressants given to patients undergoing allogeneic HSCT disturb the microbiome and the host immune system, potentially leading to dysbiosis and inflammation, and may affect immune function and bone marrow transplantation. The intestinal microbiome is a target for the development of novel therapies for GvHD. Lactobacillus species are widely used supplements to induce production of antimicrobial and anti-inflammatory factors.

Methods

We determined the effect of the combination of Lactobacillus acidophilus and FK506 on GvHD following major histocompatibility complex-mismatched bone marrow transplantation.

Results

The combination treatment suppressed IFN-γ and IL-17-producing T cell differentiation, but increased Foxp3⁺Treg differentiation and IL-10 production. Also, the combination treatment and combination treated-induced Treg cells modulated the proliferation of murine alloreactive T cells in vitro. Additionally, the combination treatment upregulated Treg-related genes—Nt5e, Foxp3, Ikzf2, Nrp1 and Itgb8—in murine CD4⁺-T cells. The combination treatment also alleviated GvHD clinically and histopathologically by controlling the effector T cell and Treg balance in vivo. Moreover, the combination treatment decreased Th17 differentiation significantly and significantly upregulated Foxp3 and IL-10 expression in peripheral blood mononuclear cells from healthy controls and liver transplantation (LT) patients.

Conclusions

Therefore, the combination of L. acidophilus and FK506 is effective and safe for patients undergoing allogeneic hematopoietic stem cell transplantation.

Bifidobacterium lactis BL-99 protects mice with osteoporosis caused by colitis via gut inflammation and gut microbiota regulation

Patients diagnosed with inflammatory bowel disease or related conditions also frequently suffer from osteoporosis as a consequence of changes in the intestinal microenvironment and consequent dysbiosis. We hypothesized that anti-inflammatory probiotic treatment would be sufficient to alleviate intestinal inflammation and thereby prevent the development of osteoporosis. To that end, the ability of Bifidobacterium lactis BL-99 administration to protect against bone loss in an experimental model of dextran sodium sulfate-induced ulcerative colitis (UC) was analyzed, and the underlying molecular mechanisms were interrogated in detail. The results of these analyses revealed that BL-99 administration suppressed colitis-associated weight loss (P < 0.05), disease activity index scores, and the production of proinflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-17) (P < 0.05). Colon tissue pathological sections similarly revealed BL-99-mediated reductions in tissue injury severity. Micro-computed tomography (Micro-CT) analyses further exhibited significant improvements in percent bone volume (BV/TV) as well as trabecular number and thickness in BL-99-treated animals (P < 0.05). Such probiotic supplementation also resulted in pronounced changes in the composition of the gut microbiota. Moreover, BL-99 intervention markedly increased the expression of intestinal barrier-related proteins (Claudin-1, MUC2, ZO-1, and Occludin). Together, these results suggest that BL-99 can be utilized as a beneficial probiotic preparation to prevent the incidence of osteoporosis in UC patients owing to its ability to shape the intestinal microflora and to suppress inflammatory cytokine production.

The Lactobacillus as a Probiotic: Focusing on Liver Diseases

Over the past decade, scientific evidence for the properties, functions, and beneficial effects of probiotics for humans has continued to accumulate. Interest in the use of probiotics for humans has increased tremendously. Among various microorganisms, probiotics using bacteria have been widely studied and commercialized, and, among them, Lactobacillus is representative. This genus contains about 300 species of bacteria (recently differentiated into 23 genera) and countless strains have been reported. They improved a wide range of diseases including liver disease, gastrointestinal diseases, respiratory diseases, and autoimmune diseases. Here, we intend to discuss in depth the genus Lactobacillus as a representative probiotic for chronic liver diseases.

"Osteomicrobiology": The Nexus Between Bone and Bugs

A growing body of scientific evidence supports the notion that gut microbiota plays a key role in the regulation of various physiological and pathological processes related to human health. Recent findings have now established that gut microbiota also contributes to the regulation of bone homeostasis. Studies on animal models have unraveled various underlying mechanisms responsible for gut microbiota-mediated bone regulation. Normal gut microbiota is thus required for the maintenance of bone homeostasis. However, dysbiosis of gut microbiota communities is reported to be associated with several bone-related ailments such as osteoporosis, rheumatoid arthritis, osteoarthritis, and periodontitis. Dietary interventions in the form of probiotics, prebiotics, synbiotics, and postbiotics have been reported in restoring the dysbiotic gut microbiota composition and thus could provide various health benefits to the host including bone health. These dietary interventions prevent bone loss through several mechanisms and thus could act as potential therapies for the treatment of bone pathologies. In the present review, we summarize the current knowledge of how gut microbiota and its derived microbial compounds are associated with bone metabolism and their roles in ameliorating bone health. In addition to this, we also highlight the role of various dietary supplements like probiotics, prebiotics, synbiotics, and postbiotics as promising microbiota targeted interventions with the clinical application for leveraging treatment modalities in various inflammatory bone pathologies.

Probiotics and Isoflavones as a Promising Therapeutic for Calcium Status and Bone Health: A Narrative Review

Probiotics have potential clinical effects for treating and preventing osteoporosis. Meanwhile, isoflavones have attracted much attention due to their ability to prevent postmenopausal symptoms. Research has established that probiotics and isoflavones can regulate hormones, immune cells, and the gastrointestinal system, acting as links in the gut-bone axis. However, combining the effects of probiotics and isoflavones on calcium status and bone health is a more novel and a still-evolving research area. Lactobacillus and Bifidobacterium are the foremost strains that influence bone health to a significant extent. Among the isoflavones, daidzein, genistein, and the metabolites of genistein (such as equol) stimulate bone formation. It can be concluded that probiotics and isoflavones promote bone health by regulating calcium uptake, gut microbiota, and various metabolic pathways that are associated with osteoblast activity and bone formation. Nevertheless, further experiments of probiotics and isoflavones are still necessary to confirm the association between calcium bioavailability and bone health.

Lactobacillus plantarum TWK10 Attenuates Aging-Associated Muscle Weakness, Bone Loss, and Cognitive Impairment by Modulating the Gut Microbiome in Mice

In humans, aging is characterized by the progressive decline in biological, physiological, and psychological functions, and is a major risk factor in the development of chronic diseases. Therefore, the development of strategies aimed at attenuating aging-related disorders and promoting healthy aging is critical. In a previous study, we have demonstrated that Lactobacillus plantarum TWK10 (TWK10), a probiotic strain isolated from Taiwanese pickled cabbage, improved muscle strength, exercise endurance, and overall body composition in healthy humans. In this study, the effect of TWK10 on the progression of age-related impairments was investigated in mice. We found that TWK10 not only enhanced muscle strength in young mice, but also prevented the aging-related loss of muscle strength in aged mice, which was accompanied by elevated muscle glycogen levels. Furthermore, TWK10 attenuated the aging-associated decline in learning and memory abilities, as well as bone mass. Further analyses of gut microbiota using next-generation sequencing (NGS) of the 16S rRNA gene showed that the pattern of gut microbial composition was clearly altered following 8 weeks of TWK10 administration. TWK10-treated mice also experienced an increase in short-chain fatty acid (SCFA)-producing bacteria and higher overall levels of gut SCFA. Furthermore, TWK10 administration to some extent reversed the aging-associated accumulation of pathogenic bacterial taxa. In conclusion, TWK10 could be viewed as a potential therapeutic agent that attenuates aging-related disorders and provides health benefits by modulating the imbalance of gut microbiota.

Antimicrobial-induced oral dysbiosis exacerbates naturally occurring alveolar bone loss

Periodontitis-mediated alveolar bone loss is caused by dysbiotic shifts in the commensal oral microbiota that upregulate proinflammatory osteoimmune responses. The study purpose was to determine whether antimicrobial-induced disruption of the commensal microbiota has deleterious effects on alveolar bone. We administered an antibiotic cocktail, minocycline, or vehicle-control to sex-matched C57BL/6T mice from age 6- to 12 weeks. Antibiotic cocktail and minocycline had catabolic effects on alveolar bone in specific-pathogen-free (SPF) mice. We then administered minocycline or vehicle-control to male mice reared under SPF and germ-free conditions, and we subjected minocycline-treated SPF mice to chlorhexidine oral antiseptic rinses. Alveolar bone loss was greater in vehicle-treated SPF versus germ-free mice, demonstrating that the commensal microbiota drives naturally occurring alveolar bone loss. Minocycline- versus vehicle-treated germ-free mice had similar alveolar bone loss outcomes, implying that antimicrobial-driven alveolar bone loss is microbiota dependent. Minocycline induced phylum-level shifts in the oral bacteriome and exacerbated naturally occurring alveolar bone loss in SPF mice. Chlorhexidine further disrupted the oral bacteriome and worsened alveolar bone loss in minocycline-treated SPF mice, validating that antimicrobial-induced oral dysbiosis has deleterious effects on alveolar bone. Minocycline enhanced osteoclast size and interface with alveolar bone in SPF mice. Neutrophils and plasmacytoid dendritic cells were upregulated in cervical lymph nodes of minocycline-treated SPF mice. Paralleling the upregulated proinflammatory innate immune cells, minocycline therapy increased TH 1 and TH 17 cells that have known pro-osteoclastic actions in the alveolar bone. This report reveals that antimicrobial perturbation of the commensal microbiota induces a proinflammatory oral dysbiotic state that exacerbates naturally occurring alveolar bone loss.

Novel microbiota-related gene set enrichment analysis identified osteoporosis associated gut microbiota from autoimmune diseases

INTRODUCTION

Gut microbiota is now considered to be a hidden organ that interacts bidirectionally with cellular responses in numerous organs belonged to the immune, bone, and nervous systems. Here, we aimed to investigate the relationships between gut microbiota and complex diseases by utilizing multiple publicly available genome-wide association.

MATERIALS AND METHODS

We applied a novel microbiota-related gene set enrichment analysis approach to detect the associations between gut microbiota and complex diseases by processing genome-wide association studies (GWASs) data sets of six autoimmune diseases (including celiac disease (CeD), inflammatory bowel diseases (IBD), multiple sclerosis (MS), primary biliary cirrhosis (PBC), type 1 diabetes (T1D) and primary sclerosing cholangitis (PSC)) and osteoporosis (OP).

RESULTS

The family Oxalobacteraceae and genus Candidatus_Soleaferrea were found to be correlated with all of the six autoimmune diseases (FDR adjusted P < 0.05). Moreover, we observed that the six autoimmune diseases except PBC shared 3 overlapping features (including family Peptostreptococcaceae, order Gastranaerophilales and genus Romboutsia). For all of the six autoimmune diseases and BMDs (LS-BMD and TB-BMD), an association signal was observed for genus Candidatus_Soleaferrea (FDR adjusted P < 0.05). Notably, FA / FN-BMD shared the maximum number of overlapping microbial features (e.g., genus Ruminococcaceae_UCG009, Erysipelatoclostridium and Ruminococcaceae_UCG013).

CONCLUSION

Our study found that part of the gut microbiota could be novel regulators of BMDs and autoimmune diseases via the effects of its metabolites and may lead to a better understanding of the role played by gut microbiota in the communication of the microbiota-skeletal/immune-gut axis.

Lactobacillus intestinalis YT2 restores the gut microbiota and improves menopausal symptoms in ovariectomized rats

There are many studies focusing on the alleviation of menopausal symptoms; however, little is known about the role of gut microorganisms in menopausal symptoms. Ovariectomized (OVX) rats were administered a novel strain (YT2) of Lactobacillus intestinalis (a species with significantly reduced abundance in OVX rats) and the potential probiotic effect on the improvement of menopausal symptoms was evaluated. Of note, the gut microbial composition completely shifted after ovariectomy in rats. Treatment with L. intestinalis YT2 significantly alleviated menopausal symptoms, such as increased fat mass, decreased bone mineral density, increased pain sensitivity, depression-like behaviour, and cognitive impairment. Additionally, the administration of L. intestinalis YT2 restored the intestinal microbial composition, including an increased Firmicutes/Bacteroides ratio. L. intestinalis YT2 also promoted gut barrier integrity by increasing the mRNA levels of tight junction-related markers. In conclusion, L. intestinalis YT2 treatment alleviated menopausal symptoms via the modulation of the gut microbiota. Importantly, these results suggest that L. intestinalis YT2 should be considered as a therapeutic probiotic agent for menopausal women.

Increased frequency of Th17 cells and IL-17 levels are associated with low bone mineral density in postmenopausal women

Osteoporosis is one of the chronic and often neglected bone diseases in aging postmenopausal women that affect the quality of life. Studies on ovariectomized mice models indicated the reciprocal role of Th17 cells and Treg cells in the aetiology of osteoporosis. While Th17 cells promote osteoclastogenesis, Treg cells exhibit anti-osteoclastogenic activity. This exploratory study aimed to determine the difference in the frequency of these T-cell subtypes in pre-and postmenopausal women and to examine their association with BMD. In our study, the frequency of Treg cells, analyzed by flow cytometry, did not differ between pre-and postmenopausal women. However, plasma levels of IL-10 along with IL-10+CD4+T cells were higher in post- compared to premenopausal women. The frequency of Th17 cells was higher in postmenopausal women irrespective of their BMD, however, only postmenopausal women with low BMD had elevated IL-17 levels and their T-scores were associated with Th17 frequency. Collectively, the results suggest that estrogen insufficiency in postmenopausal women may lead to increased Th17 cell frequency and elevated IL-17 levels which are associated with low BMD. This study highlights, Th17 cells and IL-17 as key players in the pathogenesis of osteoporosis and they can be the potential targets for immunotherapy in the treatment of osteoporosis.

Probiotics as a New Regulator for Bone Health: A Systematic Review and Meta-Analysis

Despite the proposed role of the gut microbiota-bone axis, findings on the association between probiotic consumption and bone health are conflicting. This systematic review aimed to assess the effect of probiotic consumption on bone health parameters. A systematic literature search of relevant reports published in PubMed/Medline, Web of Science, SCOPUS, EMBASE, and Google scholar before December 2020 was conducted. All clinical trials or experimental studies, which examined the relationship between probiotic consumption and bone health parameters, were included. No limitation was applied during the search. After screening articles based on inclusion criteria, 44 studies remained. In clinical trials, probiotic consumption affects bone health parameters such as serum calcium levels (3.82; 95% CI: 1.05, 6.59 mmol/l), urinary calcium levels (4.85; 95% CI: 1.16, 8.53 mmol/l), and parathyroid hormone (PTH) levels (−5.53; 95% CI: −9.83, −0.86 ng/l). In most studies, Lactobacillus species such as L. helveticus, L. reuteri, and L. casei were consumed and women aged 50 years or older were assessed. Spinal and total hip bone mineral density (BMD) was not affected significantly by probiotic consumption. In 37 animal experiments, probiotic or symbiotic feeding mostly had effects on bone health parameters. Some strains of Bifidobacterium and Lactobacillus including L. reuteri, L. casei, L. paracasei, L. bulgaricus, and L. acidophilus have indicated beneficial effects on bone health parameters. In conclusion, this systematic review and meta-analysis indicate that probiotic supplementation might improve bone health. Further studies are needed to decide on the best probiotic species and appropriate dosages.

Probiotics ameliorate alveolar bone loss by regulating gut microbiota

OBJECTIVES

Oestrogen deficiency is an aetiological factor of postmenopausal osteoporosis (PMO), which not only decreases bone density in vertebrae and long bone but also aggravates inflammatory alveolar bone loss. Recent evidence has suggested the critical role of gut microbiota in osteoimmunology and its influence on bone metabolisms. The present study aimed to evaluate the therapeutic effects of probiotics on alveolar bone loss under oestrogen-deficient condition.

MATERIALS AND METHODS

Inflammatory alveolar bone loss was established in ovariectomized (OVX) rats, and rats were daily intragastrically administered with probiotics until sacrifice. Gut microbiota composition, intestinal permeability, systemic immune status and alveolar bone loss were assessed to reveal the underlying correlation between gut microbiota and bone metabolisms.

RESULTS

We found administration of probiotics significantly prevented inflammatory alveolar bone resorption in OVX rats. By enriching butyrate-producing genera and enhancing gut butyrate production, probiotics improved intestinal barrier and decreased gut permeability in the OVX rats. Furthermore, the oestrogen deprivation-induced inflammatory responses were suppressed in probiotics-treated OVX rats, as reflected by reduced serum levels of inflammatory cytokines and a balanced distribution of CD4+ IL-17A+ Th17 cells and CD4+ CD25+ Foxp3+ Treg cells in the bone marrow.

CONCLUSIONS

This study demonstrated that probiotics can effectively attenuate alveolar bone loss by modulating gut microbiota and further regulating osteoimmune response and thus represent a promising adjuvant in the treatment of alveolar bone loss under oestrogen deficiency.

Regulatory B Cells (Bregs) Inhibit Osteoclastogenesis and Play a Potential Role in Ameliorating Ovariectomy-Induced Bone Loss

Increasing evidence in recent years has suggested that regulatory B cells (Bregs) are one of the crucial modulators in various inflammatory disease conditions. However, no study to date has investigated the significance of Bregs in modulating osteoclastogenesis. To the best of our knowledge, in the present study, we for the first time examined the anti-osteoclastogenic potential of Bregs under in vitro conditions and observed that Bregs suppress RANKL-induced osteoclastogenesis in a dose-dependent manner. We further elucidated the mechanism behind the observed suppression of osteoclasts differentiation via Bregs. Our results clearly suggested that the observed anti-osteoclastogenic property of Bregs is mediated via the production of IL-10 cytokine. Next, we explored whether Bregs have any role in mediating inflammatory bone loss under post-menopausal osteoporotic conditions in ovx mice. Remarkably, our in vivo data clearly suggest that the frequencies of both CD19+IL-10+ Bregs and CD19+CD1dhiCD5+IL-10+ "B10" Bregs were significantly reduced in case of osteoporotic mice model. Moreover, we also found a significant reduction in serum IL-10 cytokine levels in osteoporotic mice, thereby further supporting our observations. Taken together, the present study for the first time establishes the direct role of regulatory B cells in modulating osteoclastogenesis in vitro. Further, our in vivo data suggest that modulations in the percentage of Bregs population along with its reduced potential to produce IL-10 might further exacerbate the observed bone loss in ovx mice.

Cell-free culture supernatant of Lactobacillus curvatus Wikim38 inhibits RANKL-induced osteoclast differentiation and ameliorates bone loss in ovariectomized mice

This study was conducted to investigate the inhibitory effects of the cell-free culture supernatant of Lactobacillus curvatus Wikim 38 (LC38-CS) on RANKL-induced osteoclast differentiation and bone loss in a mice model of ovariectomy-induced post-menopausal osteoporosis. LC38-CS inhibited the RANKL-induced differentiation of bone marrow-derived macrophages (BMDMs) into osteoclasts in a dose-dependent manner. F-actin ring formation and bone resorption were also reduced by LC38-CS treatment of RANKL-treated BMDMs. In addition, LC38-CS decreased the RANKL-induced activation of the TRAF6/NF-κB/MAPKs axis at the early stage and the expression of osteoclastogenesis-related genes in BMDMs treated with RANKL. PRMT1 and ADMA levels, new biomarkers for osteoclastogenesis, were decreased by LC38-CS treatment. The administration of LC38-CS increased bone volume and bone mineral density in ovariectomized mice in μ-CT analysis. These findings suggest that LC38-CS inhibited RANKL-induced osteoclast differentiation by the downregulation of molecular mechanisms and exerted anti-osteoporotic effects.

Lactobacillus casei CCFM1074 Alleviates Collagen-Induced Arthritis in Rats via Balancing Treg/Th17 and Modulating the Metabolites and Gut Microbiota

Gut microbiota and their influence on metabolites are receiving increasing attentions in autoimmune diseases including rheumatoid arthritis (RA). Probiotics become a promising manipulator to prevent or attenuate the progression of arthritis, some evidences suggesting that lactobacilli treatment influence the responses to RA therapy but the underlying mechanisms are limited. By using a collagen-induced arthritis (CIA) rats, the study assessed the effects of two L. casei strains (CCFM1074, CCFM1075) on the immune responses, gut microbiota and plasma metabolites via an integrated cross-omics approach including fecal 16S rRNA high-throughput sequencing and plasma metabolomics. The genome of the two strains was analyzed and compared using whole-genome sequencing approach to further confirm biology functions. CCFM1074 reduced arthritic symptoms while CCFM1075 did not, though both strains down-regulated the plasma IL-6 and Th17 cells proportion. CCFM1074 enhanced the proportion of Treg cells in mesenteric lymph nodes which was significantly associated with SCFAs upregulation, as well as with genomic evidence that CCFM1074 possesses more functional genes involved in carbohydrate metabolism. Moreover, CCFM1074 regulated the gut microbiota, including modulating community structure, decreasing the abundance of Alistipes and Parabacteroides and increasing the abundance of Oscillibacter. The differential metabolites modulated by CCFM1074 including eicosapentaenoic acid and docosapentaenoic acid which involved in unsaturated fatty acids metabolism. Furthermore, alterations of gut microbial community were correlated with the plasma metabolome. In summary, L. casei CCFM1074 alleviated arthritis via rebalancing gut microbiota, immune responses and plasma metabolites.

An Exopolysaccharide Produced by Bifidobacterium longum 35624® Inhibits Osteoclast Formation via a TLR2-Dependent Mechanism

The probiotic Bifidobacterium longum subsp. longum 35624® (B. longum 35624®), with its surface exopolysaccharide (EPS624), has previously been demonstrated to induce immunoregulatory responses in the host and may, therefore, be a novel approach to prevent bone loss in inflammatory conditions such as post-menopausal osteoporosis (PMO). The aim of this study was to investigate the effect of EPS624 on osteoclast and osteoblast differentiation and to assess the potential of B. longum 35624® to prevent bone loss in vivo. In vitro cell assays were used to assess the impact of EPS624 on osteoclast and osteoblast differentiation. The potential of two probiotic B. longum 35624® strains, including an EPS-deficient strain, for preventing ovariectomy (Ovx)-induced bone loss was assessed in a murine model. EPS624 prevented osteoclast formation from murine bone marrow precursors under both normal and TNFα-induced inflammatory conditions and modestly increased mineralized matrix deposition in osteogenic cell cultures. However, in the presence of an anti-TLR2 blocking antibody, or in MyD88^-/- osteoclast precursors, the inhibitory effect of EPS624 on osteoclast formation was diminished or completely prevented, respectively. Moreover, EPS624 induced IL-10 production in osteoclast precursors in a TLR2-dependent manner, although IL-10 was dispensable in the EPS624-mediated inhibition of osteoclast formation. In addition, EPS624-producing B. longum 35624® partially prevented bone loss in Ovx mice when administered by oral gavage. This study introduced EPS624 as a potential anti-resorptive therapy, although optimal in vivo delivery of the probiotic strain for treating low-grade inflammatory diseases such as PMO remains to be determined.

Clostridium butyricum Alleviates Gut Microbiota Alteration-Induced Bone Loss after Bariatric Surgery by Promoting Bone Autophagy

Bariatric surgery is the most common and effective treatment of severe obesity; however, these bariatric procedures always result in detrimental effects on bone metabolism by underlying mechanisms. This study aims to investigate the skeletal response to bariatric surgery and to explore whether Clostridium butyricum alleviates gut microbiota alteration-induced bone loss after bariatric surgery. Consequently, male SD rats received Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery, respectively, followed by body weight recording. The bone loss after bariatric surgery was further determined by dual-energy X-ray absorptiometry (DXA), micro-CT measurement, histologic analyses, and Western blot. Besides, 16S rDNA gene sequencing was performed to determine the gut microbiota alteration after surgery, and intervention with fecal microbiota from RYGB donor was conducted in obese SD rats, followed by C. butyricum administration. Accordingly, rats in the RYGB and SG groups maintained sustained weight loss, and DXA and micro-CT measurement further demonstrated significant bone loss after bariatric surgery. Besides, histologic and Western blot analyses validated enhanced osteoclastogenesis and inhibited osteoblastogenesis and defective autophagy after surgery. The 16S rDNA gene sequencing suggested a significant alteration of gut microbiota composition in the RYGB group, and intervention with fecal microbiota from RYGB donor further determined that this kind of alteration contributed to the bone loss after RYGB. Meanwhile, C. butyricum might protect against this postoperative bone loss by promoting osteoblast autophagy. In summary, this study suggests novel mechanisms to clarify the skeletal response to bariatric surgery and provides a potential candidate for the treatment of bone disorder among bariatric patients. SIGNIFICANCE STATEMENT: The significance of this study is the discovery of obvious bone loss and defective autophagy after bariatric surgery. Besides, it is revealed that gut microbiota alterations could be the reason for impaired bone mass after bariatric surgery. Furthermore, Clostridium butyricum could alleviate the gut microbiota alteration-induced bone loss after bariatric surgery by promoting osteoblast autophagy.

Post-menopausal Osteoporosis and Probiotics

Postmenopausal osteoporosis (PMO) is characterized by low bone mass and structural deterioration of bone tissue with increased risk of fracture in postmenopausal women. It is due to the deficiency of estrogen production after menopause, which causes the imbalance in the bone remodeling process where resorption/formation skewed more towards resoption, which leads to bone loss. It causes high morbidity and severe health complication among the affected women. The current PMO therapy has many unwanted side effects and even increases the possibility of tumorigenesis. Therefore, an alternative therapy that is safe and effective is required. Probiotics are dietary supplements consisting of beneficial microbes and when administered in an adequate amount, confer a health benefit to the host. Recent scientific evidences suggested the link between the intestinal microbiota and bone health. This review discusses the process of bone remodeling and the role of intestinal microbiota on the bone metabolism of the host. Further, it summarizes the recent studies of probiotic on an animal model of PMO and also in post postmenopausal women.

T cell-depleting nanoparticles ameliorate bone loss by reducing activated T cells and regulating the Treg/Th17 balance

Estrogen deficiency is one of the most frequent causes of osteoporosis in postmenopausal women. Under chronic inflammatory conditions caused by estrogen deficiency, activated T cells contribute to elevated levels of proinflammatory cytokines, impaired osteogenic differentiation capabilities of bone marrow mesenchymal stem cells (BMMSCs), and disturbed regulatory T cell (Treg)/Th17 cell balance. However, therapeutic strategies that re-establish immune homeostasis in this disorder have not been well developed. Here, we produced T cell-depleting nanoparticles (TDNs) that ameliorated the osteopenia phenotype and rescued the osteogenic deficiency of BMMSCs in ovariectomized (OVX) mice. TDNs consist of monocyte chemotactic protein-1 (MCP-1)-encapsulated mesoporous silica nanoparticles as the core and Fas-ligand (FasL) as the corona. We showed that the delicate design of the TDNs enables rapid release of MCP-1 to recruit activated T cells and then induces their apoptosis through the conjugated FasL both in vitro and in vivo. Apoptotic signals recognized by macrophages help skew the Treg/Th17 cell balance and create an immune tolerant state, further attenuating the osteogenic deficiency of BMMSCs and the osteopenia phenotype. Mechanistically, we found that the therapeutic effects of TDNs were partially mediated by apoptotic T cell-derived extracellular vesicles (ApoEVs), which promoted macrophage transformation towards the M2 phenotype. These findings demonstrate that TDNs may represent a promising strategy for treating osteoporosis and other immune disorders.

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A delicate nanoparticle was prepared which can induce the apoptosis of activated T cells.

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The T cell-depleting nanoparticles establish an immune tolerance microenvironment and ameliorate bone loss in OVX mice.

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T cell-derived apoptotic extracellular vesicles participated in the amelioration of osteopenia.