The Human Gut Microbiota: A Key Mediator of Osteoporosis and Osteogenesis

Cutting-edge microneedle innovations: Transforming the landscape of cardiovascular and metabolic disease management

Cardiovascular diseases (CVDs) and metabolic disorders (MDs) have surfaced as formidable challenges to global health, significantly imperiling human well-being. Recently, microneedles (MNs) have garnered substantial interest within the realms of CVD and MD research. Offering a departure from conventional diagnostic and therapeutic methodologies, MNs present a non-invasive, safe, and user-friendly modality for both monitoring and treatment, thereby marking substantial strides and attaining pivotal achievements in this avant-garde domain, while also unfurling promising avenues for future inquiry. This thorough review encapsulates the latest developments in employing MNs for both the surveillance and management of CVDs and MDs. Initially, it succinctly outlines the foundational principles and approaches of MNs in disease surveillance and therapy. Subsequently, it delves into the pioneering utilizations of MNs in the surveillance and management of CVDs and MDs. Ultimately, this discourse synthesizes and concludes the primary findings of this investigation, additionally prognosticating on the trajectory of MN technology.

Oral Propolis Nanoemulsions Modulate Gut Microbiota to Balance Bone Remodeling for Enhanced Osteoporosis Therapy

The discovery of the bone-gut axis linking bone metabolism to gut microbiota (GM) dysbiosis has revolutionized our understanding of managing degenerative skeletal diseases. Targeting GM regulation has emerged as a promising approach to osteoporosis treatment. Herein, we develop propolis nanoemulsions (PNEs) with enhanced gastrointestinal stability and oral bioavailability for GM-based osteoporosis therapy. Orally administered PNEs exhibit superior antiosteoporosis efficacy in an ovariectomized (OVX) mouse model by modulating the GM structure and metabolites and restoring the intestinal barrier function. Multiomics analysis reveals that a reduction in Streptococcus abundance and an increase in the GM metabolite l-arginine are key factors in osteoporosis management. These changes suppress osteoclast activity and enhance osteoblast function, leading to balanced bone remodeling and, thus, significant antiosteoporotic effects via the gut-bone axis. Our results deepen insights into the intricate relationship between GM and bone remodeling, suggesting a promising strategy that maintains the homeostasis of the GM structure and metabolite for osteoporosis treatment.

Health benefits and risks of fermented foods-the PIMENTO initiative

Worldwide, fermented foods (FF) are recognized as healthy and safe. Despite the rapid increase of research papers, there is a lack of systematic evaluation of the health benefits and risks of FF. The COST Action CA20128 "Promoting innovation of fermented foods" (PIMENTO) aims to provide a comprehensive assessment on the available evidence by compiling a set of 16 reviews. Seven reviews will cover clinical and biological endpoints associated with major health indicators across several organ systems, including the cardiovascular, gastrointestinal, neurological, immune, and skeletal systems. Nine reviews will address broader biological questions associated with FF including bioactive compounds and vitamin production, nutrient bioavailability and bioaccessibility, the role of FF in healthy diets and personalized nutrition, food safety, regulatory practices, and finally, the health properties of novel and ethnic FF. For each outcome assessed in the reviews, an innovative approach will be adopted based on EFSA's published guidance for health claim submissions. In particular, each review will be composed of three parts: (1) a systematic review of available human studies; (2) a non-systematic review of the mechanism of action related to the clinical endpoints measured by the human studies identified in part 1; and (3) a non-systematic review of the characterization of the FF investigated in the human studies identified in part 1. The evidence and research gaps derived from the reviews will be summarized and published in the form of a strategic road map that will pave the way for future research on FF.

Analysis of the causal relationship between gut microbiota and bone remodeling growth factor from the gene association

BACKGROUND

A growing body of evidence indicates a close association between the gut microbiota (GM) and the bone remodeling (BR) process, raising suspicions that the GM may actively participate in BR by modulating the levels of growth factors. However, the precise causal relationship between them remains unclear. Due to many confounding factors, many microorganisms related to BR growth factors have not been identified. We aimed to elucidate the causal relationship between the GM and BR growth factors.

METHODS

We evaluated the genome-wide association study (GWAS) summary statistics for GM and five common growth factors associated with BR: namely, bone morphogenetic proteins (BMP), transforming growth factors(TGF), insulin growth factors (IGFs), epidermal growth factors (EGFs), and fibroblast growth factors (FGF). The causal relationship between the GM and BR growth factors was studied by double-sample Mendelian randomized analysis. We used five Mendelian randomization (MR) methods, including inverse variance-weighted (IVW), MR-Egger, simple mode, weighted median, and weighted model methods.

RESULTS

Through MR analysis, a total of 56 bacterial genera were co-identified as associated with BMP, TGF, IGF, EGF, and FGF. Among them, eight genera were found to have a causal relationship with multiple growth factors: Marvinbryantia was causally associated with BMP-6 (P = 0.018, OR = 1.355) and TGF-β2 (P = 0.002, OR = 1.475); Lachnoclostridium, BMP-7 (P = 0.021, OR = 0.73) and IGF-1 (P = 0.046, OR = 0.804); Terrisporobacter, TGF-β (P = 0.02, OR = 1.726) and FGF-23 levels (P = 0.016, OR = 1.76); Ruminiclostridium5, TGF-β levels (P = 0.024, OR = 0.525) and FGFR-2 (P = 0.003, OR = 0.681); Erysipelatoclostridium, TGF-β2 (P = 0.001, OR = 0.739) and EGF and its receptor (EGFR) (P = 0.012, OR = 0.795); Eubacterium_brachy_group, FGFR-2 (P = 0.045, OR = 1.153) and EGF (P = 0.013, OR = 0.7); Prevotella9 with EGFR (P = 0.022, OR = 0.818) and FGFR-2 (P = 0.011, OR = 1.233) and Faecalibacterium with FGF-23 (P = 0.02, OR = 2.053) and IGF-1 (P = 0.005, OR = 0.843).

CONCLUSION

We confirmed the causal relationship between the GM and growth factors related to BR, which provides a new perspective for the study of BR, through targeted regulation of specific bacteria to prevent and treat diseases and growth factor-mediated BR disorders.

The Brain-Gut-Bone Axis in Neurodegenerative Diseases: Insights, Challenges, and Future Prospects

Neurodegenerative diseases are global health challenges characterized by the progressive degeneration of nerve cells, leading to cognitive and motor impairments. The brain-gut-bone axis, a complex network that modulates multiple physiological systems, has gained increasing attention owing to its profound effects on the occurrence and development of neurodegenerative diseases. No comprehensive review has been conducted to clarify the triangular relationship involving the brain-gut-bone axis and its potential for innovative therapies for neurodegenerative disorders. In light of this, a new perspective is aimed to propose on the interplay between the brain, gut, and bone systems, highlighting the potential of their dynamic communication in neurodegenerative diseases, as they modulate multiple physiological systems, including the nervous, immune, endocrine, and metabolic systems. Therapeutic strategies for maintaining the balance of the axis, including brain health regulation, intestinal microbiota regulation, and improving skeletal health, are also explored. The intricate physiological interactions within the brain-gut-bone axis pose a challenge in the development of effective treatments that can comprehensively target this system. Furthermore, the safety of these treatments requires further evaluation. This review offers a novel insights and strategies for the prevention and treatment of neurodegenerative diseases, which have important implications for clinical practice and patient well-being.

The potential therapeutic role of curcumin in osteoporosis treatment: based on multiple signaling pathways

Osteoporosis is a common chronic metabolic bone disease caused by disturbances in normal bone metabolism and an imbalance between osteoblasts and osteoclasts. Osteoporosis is characterized by a decrease in bone mass and bone density, leading to increased bone fragility. Osteoporosis is usually treated with medications and surgical methods, but these methods often produce certain side effects. Therefore, the use of traditional herbal ingredients for the treatment of osteoporosis has become a focus of attention and a hot topic in recent years. Curcumin, widely distributed among herbs such as turmeric, tulip, and curcuma longa, contains phenolic, terpenoid, and flavonoid components. Modern pharmacological studies have confirmed that curcumin has a variety of functions including antioxidant and anti-inflammatory properties. In addition, curcumin positively regulates the differentiation and promotes the proliferation of osteoblasts, which play a crucial role in bone formation. Multiple studies have shown that curcumin is effective in the treatment of osteoporosis as it interacts with a variety of signaling pathway targets, thereby interfering with the formation of osteoblasts and osteoclasts and regulating the development of osteoporosis. This review summarized the key signaling pathways and their mechanisms of action of curcumin in the prevention and treatment of osteoporosis and analyzed their characteristics and their relationship with osteoporosis and curcumin. This not only proves the medicinal value of curcumin as a traditional herbal ingredient but also further elucidates the molecular mechanism of curcumin's anti-osteoporosis effect, providing new perspectives for the prevention and treatment of osteoporosis through multiple pathways.

Immune Remodeling during Aging and the Clinical Significance of Immunonutrition in Healthy Aging

Aging is associated with changes in the immune system and the gut microbiota. Immunosenescence may lead to a low-grade, sterile chronic inflammation in a multifactorial and dynamic way, which plays a critical role in most age-related diseases. Age-related changes in the gut microbiota also shape the immune and inflammatory responses. Nutrition is a determinant of immune function and of the gut microbiota. Immunonutrion has been regarded as a new strategy for disease prevention and management, including many age-related diseases. However, the understanding of the cause-effect relationship is required to be more certain about the role of immunonutrition in supporting the immune homeostasis and its clinical relevance in elderly individuals. Herein, we review the remarkable quantitative and qualitative changes during aging that contribute to immunosenescence, inflammaging and microbial dysbiosis, and the effects on late-life health conditions. Furthermore, we discuss the clinical significance of immunonutrition in the treatment of age-related diseases by systematically reviewing its modulation of the immune system and the gut microbiota to clarify the effect of immunonutrition-based interventions on the healthy aging.

Navigating the gut-bone axis: The pivotal role of Coprococcus3 in osteoporosis prevention through Mendelian randomization

Osteoporosis (OP) constitutes a notable public health concern that significantly impacts the skeletal health of the global aging population. Its prevalence is steadily escalating, yet the intricacies of its diagnosis and treatment remain challenging. Recent investigations have illuminated a profound interlink between gut microbiota (GM) and bone metabolism, thereby opening new avenues for probing the causal relationship between GM and OP. Employing Mendelian randomization (MR) as the investigative tool, this study delves into the causal rapport between 211 varieties of GM and OP. The data are culled from genome-wide association studies (GWAS) conducted by the MiBioGen consortium, in tandem with OP genetic data gleaned from the UK Biobank, BioBank Japan Project, and the FinnGen database. A comprehensive repertoire of statistical methodologies, encompassing inverse-variance weighting, weighted median, Simple mode, Weighted mode, and MR-Egger regression techniques, was adroitly harnessed for meticulous analysis. The discernment emerged that the genus Coprococcus3 is inversely associated with OP, potentially serving as a deterrent against its onset. Additionally, 21 other gut microbial species exhibited a positive correlation with OP, potentially accentuating its proclivity and progression. Subsequent to rigorous scrutiny via heterogeneity and sensitivity analyses, these findings corroborate the causal nexus between GM and OP. Facilitated by MR, this study successfully elucidates the causal underpinning binding GM and OP, thereby endowing invaluable insights for deeper exploration into the pivotal role of GM in the pathogenesis of OP.

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.

Mapping knowledge landscapes and research frontiers of gastrointestinal microbiota and bone metabolism: a text-mining study

Introduction

Extensive research efforts have been dedicated to elucidating the intricate pathways by which gastrointestinal microbiota and their metabolites exert influence on the processes of bone formation. Nonetheless, a notable gap exists in the literature concerning a bibliometric analysis of research trends at the nexus of gastrointestinal microbiota and bone metabolism.

Methods

To address this scholarly void, the present study employs a suite of bibliometric tools including online platforms, CiteSpace and VOSviewer to scrutinize the pertinent literature in the realm of gastrointestinal microbiota and bone metabolism.

Results and discussion

Examination of the temporal distribution of publications spanning from 2000 to 2023 reveals a discernible upward trajectory in research output, characterized by an average annual growth rate of 19.2%. Notably, China and the United States emerge as primary contributors. Predominant among contributing institutions are Emory University, Harvard University, and the University of California. Pacifici R from Emory University contributed the most research with 15 publications. In the realm of academic journals, Nutrients emerges as the foremost publisher, followed closely by Frontiers in Microbiology and PLOS One. And PLOS One attains the highest average citations of 32.48. Analysis of highly cited papers underscores a burgeoning interest in the therapeutic potential of probiotics or probiotic blends in modulating bone metabolism by augmenting host immune responses. Notably, significant research attention has coalesced around the therapeutic interventions of probiotics, particularly Lactobacillus reuteri, in osteoporosis, as well as the role of gastrointestinal microbiota in the etiology and progression of osteoarthritis. Keyword analysis reveals prevalent terms including gut microbiota, osteoporosis, bone density, probiotics, inflammation, SCFAs, metabolism, osteoarthritis, calcium absorption, obesity, double-blind, prebiotics, mechanisms, postmenopausal women, supplementation, risk factors, oxidative stress, and immune system. Future research endeavors warrant a nuanced exploration of topics such as inflammation, obesity, SCFAs, postmenopausal osteoporosis, skeletal muscle, oxidative stress, double-blind trials, and pathogenic mechanisms. In summary, this study presents a comprehensive bibliometric analysis of global research on the interplay between gastrointestinal microbiota and bone metabolism, offering valuable insights for scholars, particularly nascent researchers, embarking on analogous investigations within this domain.

Prediction of Osteoporotic Hip Fracture Outcome: Comparative Accuracy of 27 Immune-Inflammatory-Metabolic Markers and Related Conceptual Issues

Objectives: This study, based on the concept of immuno-inflammatory-metabolic (IIM) dysregulation, investigated and compared the prognostic impact of 27 indices at admission for prediction of postoperative myocardial injury (PMI) and/or hospital death in hip fracture (HF) patients. Methods: In consecutive HF patient (n = 1273, mean age 82.9 ± 8.7 years, 73.5% females) demographics, medical history, laboratory parameters, and outcomes were recorded prospectively. Multiple logistic regression and receiver-operating characteristic analyses (the area under the curve, AUC) were used to establish the predictive role for each biomarker. Results: Among 27 IIM biomarkers, 10 indices were significantly associated with development of PMI and 16 were indicative of a fatal outcome; in the subset of patients aged >80 years with ischaemic heart disease (IHD, the highest risk group: 90.2% of all deaths), the corresponding figures were 26 and 20. In the latter group, the five strongest preoperative predictors for PMI were anaemia (AUC 0.7879), monocyte/eosinophil ratio > 13.0 (AUC 0.7814), neutrophil/lymphocyte ratio > 7.5 (AUC 0.7784), eosinophil count < 1.1 × 109/L (AUC 0.7780), and neutrophil/albumin × 10 > 2.4 (AUC 0.7732); additionally, sensitivity was 83.1-75.4% and specificity was 82.1-75.0%. The highest predictors of in-hospital death were platelet/lymphocyte ratio > 280.0 (AUC 0.8390), lymphocyte/monocyte ratio < 1.1 (AUC 0.8375), albumin < 33 g/L (AUC 0.7889), red cell distribution width > 14.5% (AUC 0.7739), and anaemia (AUC 0.7604), sensitivity 88.2% and above, and specificity 85.1-79.3%. Internal validation confirmed the predictive value of the models. Conclusions: Comparison of 27 IIM indices in HF patients identified several simple, widely available, and inexpensive parameters highly predictive for PMI and/or in-hospital death. The applicability of IIM biomarkers to diagnose and predict risks for chronic diseases, including OP/OF, in the preclinical stages is discussed.

Probiotics: a promising intervention for osteoporosis prevention and management

Osteoporosis (OP) is a systemic skeletal disease that is characterized by low bone mass and increased fracture risk. This article explores the potential of probiotics as an adjunctive approach for the prevention and management of OP. It has been well established that the gut microbiota (GM), a complex community of microbes, plays an important role in bone health. The gut dysbiosis is linked with a higher risk of OP. However, the consumption of probiotics in adequate amounts restores gut health thus improving bone health. Probiotics may influence bone metabolism through enhanced calcium absorption, reduced inflammation, and increased bone formation. The animal and human studies demonstrate the positive effects of probiotics on bone health parameters like reduced osteoclastogenesis, bone resorption markers, osteoblast, osteocyte apoptosis, and increased bone mineral density and expression of osteoprotegerin. The current evidence suggests that probiotics can be used as an adjunctive approach along with the existing therapies for the prevention and management of OP.

Microbiota and Resveratrol: How Are They Linked to Osteoporosis?

Osteoporosis (OP), which is characterized by a decrease in bone density and increased susceptibility to fractures, is closely linked to the gut microbiota (GM). It is increasingly realized that the GM plays a key role in the maintenance of the functioning of multiple organs, including bone, by producing bioactive metabolites such as short-chain fatty acids (SCFA). Consequently, imbalances in the GM, referred to as dysbiosis, have been identified with a significant reduction in beneficial metabolites, such as decreased SCFA associated with increased chronic inflammatory processes, including the activation of NF-κB at the epigenetic level, which is recognized as the main cause of many chronic diseases, including OP. Furthermore, regular or long-term medications such as antibiotics and many non-antibiotics such as proton pump inhibitors, chemotherapy, and NSAIDs, have been found to contribute to the development of dysbiosis, highlighting an urgent need for new treatment approaches. A promising preventive and adjuvant approach is to combat dysbiosis with natural polyphenols such as resveratrol, which have prebiotic functions and ensure an optimal microenvironment for beneficial GM. Resveratrol offers a range of benefits, including anti-inflammatory, anti-oxidant, analgesic, and prebiotic effects. In particular, the GM has been shown to convert resveratrol, into highly metabolically active molecules with even more potent beneficial properties, supporting a synergistic polyphenol-GM axis. This review addresses the question of how the GM can enhance the effects of resveratrol and how resveratrol, as an epigenetic modulator, can promote the growth and diversity of beneficial GM, thus providing important insights for the prevention and co-treatment of OP.

New insights into dairy management and the prevention and treatment of osteoporosis: The shift from single nutrient to dairy matrix effects-A review

Dairy is recognized as a good source of calcium, which is important for preventing osteoporosis. However, the relationship between milk and bone health is more complex than just calcium supplementation. It is unwise to focus solely on observing the effects of a single nutrient. Lactose, proteins, and vitamins in milk, as well as fatty acids, oligosaccharides, and exosomes, all work together with calcium to enhance its bioavailability and utilization efficiency through various mechanisms. We evaluate the roles of dairy nutrients and active ingredients in maintaining bone homeostasis from the perspective of the dairy matrix effects. Special attention is given to threshold effects, synergistic effects, and associations with the gut-bone axis. We also summarize the associations between probiotic/prebiotic milk, low-fat/high-fat milk, lactose-free milk, and fortified milk with a reduced risk of osteoporosis and discuss the potential benefits and controversies of these dairy products. Moreover, we examine the role of dairy products in increasing peak bone mass during adolescence and reducing bone loss in old age. It provides a theoretical reference for the use of dairy products in the accurate prevention and management of osteoporosis and related chronic diseases and offers personalized dietary recommendations for bone health in different populations.

Cedrol alleviates postmenopausal osteoporosis in rats through inhibiting the activation of the NF-κB signaling pathway

Pharmacological studies have shown that Cedrol (CE) exhibits extensive biological activities, including anti-inflammatory and analgesic. Moreover, it can inhibit the NF-κB pathway and the expression of various associated proteins. This study aimed to investigate the role of CE in postmenopausal osteoporosis. The results showed that intragastric administration of CE (10 and 20 mg/kg) significantly improved the bone microstructure damage and increased bone mineral density, trabecular bone volume, and bone trabecular thickness in ovariectomized (OVX) rats (p < 0.05). CE treatment additionally made a well-organized arrangement of bone trabeculae and improved its thickness and density. Compared with the OVX group, the levels of tartrate-resistant acid phosphatase from 5b and C-terminal telopeptide of type I collagen were significantly reduced by 42.75% and 49.27% in the OVX + CE rats (p < 0.05). TRAP staining visually showed that the number of osteoclasts in the femur tissue of CE-treated rats was less than that of the OVX group. The expressions of nuclear factor of activated T-cells, cytoplasmic 1, acid phosphatase 5, and cathepsin K in OVX + CE rats were significantly decreased by 51.61%, 46.07%, and 50.34% compared to the OVX group (p < 0.01). In addition, CE intervention effectively reduced the phosphorylation levels of P65 and IκBα and inhibited the NF-κB signaling pathway. Meanwhile, CE diminished the number of multinucleated osteoclasts induced by receptor activator for nuclear factor-κB ligand and hindered cell fusion as well as nuclear translocation of osteoclast precursor cells P65. In conclusion, CE inhibits osteoclastogenesis by suppressing the activation of the NF-κB signaling pathway, thereby alleviating postmenopausal osteoporosis.

A comprehensive review and advanced biomolecule-based therapies for osteoporosis

BACKGROUND

The prevalence of osteoporosis (OP) on a global scale is significantly elevated that causes life threatening issues. The potential of groundbreaking biomolecular therapeutics in the field of OP is highly encouraging. The administration of biomolecular agents has the potential to mitigate the process of bone demineralization while concurrently augmenting the regenerative capacity of bone tissue, thereby facilitating a personalized therapeutic approach. Biomolecules-based therapies showed promising results in term of bone mass protection and restoration in OP.

AIM OF REVIEW

We summarized the recent biomolecular therapies with notable progress in clinical, demonstrating the potential to transform illness management. These treatments frequently utilize different biomolecule based strategies. Biomolecular therapeutics has a targeted character, which results in heightened specificity and less off-target effects, ultimately leading to increased patient outcomes. These aspects have the capacity to greatly enhance the management of OP, thus resulting in a major enhancement in the quality of life encountered by individuals affected by this condition.

A decade of insight: bibliometric analysis of gut microbiota's role in osteoporosis (2014-2024)

Purpose

Osteoporosis represents a profound challenge to public health, underscoring the critical need to dissect its complex etiology and identify viable targets for intervention. Within this context, the gut microbiota has emerged as a focal point of research due to its profound influence on bone metabolism. Despite this growing interest, the literature has yet to see a bibliometric study addressing the gut microbiota's contribution to both the development and management of osteoporosis. This study aims to fill this gap through an exhaustive bibliometric analysis. Our objective is to uncover current research hotspots, delineate key themes, and identify future research trends. In doing so, we hope to provide direction for future studies and the development of innovative treatment methods.

Methods

Relevant publications in this field were retrieved from the Web of Science Core Collection database. We used VOSviewer, CiteSpace, an online analysis platform and the R package "Bibliometrix" for bibliometric analysis.

Results

A total of 529 publications (including 351 articles and 178 reviews) from 61 countries, 881 institutions, were included in this study. China leads in publication volume and boast the highest cumulative citation. Shanghai Jiao Tong University and Southern Medical University are the leading research institutions in this field. Nutrients contributed the largest number of articles, and J Bone Miner Res is the most co-cited journal. Of the 3,166 scholars who participated in the study, Ohlsson C had the largest number of articles. Li YJ is the most co-cited author. "Probiotics" and "inflammation" are the keywords in the research.

Conclusion

This is the first bibliometric analysis of gut microbiota in osteoporosis. We explored current research status in recent years and identified frontiers and hot spots in this research field. We investigate the impact of gut microbiome dysregulation and its associated inflammation on OP progression, a topic that has garnered international research interest in recent years. Additionally, our study delves into the potential of fecal microbiota transplantation or specific dietary interventions as promising avenues for future research, which can provide reference for the researchers who focus on this research filed.

Natural Compounds for Bone Remodeling: A Computational and Experimental Approach Targeting Bone Metabolism-Related Proteins

Osteoporosis, characterized by reduced bone density and increased fracture risk, affects over 200 million people worldwide, predominantly older adults and postmenopausal women. The disruption of the balance between bone-forming osteoblasts and bone-resorbing osteoclasts underlies osteoporosis pathophysiology. Standard treatment includes lifestyle modifications, calcium and vitamin D supplementation and specific drugs that either inhibit osteoclasts or stimulate osteoblasts. However, these treatments have limitations, including side effects and compliance issues. Natural products have emerged as potential osteoporosis therapeutics, but their mechanisms of action remain poorly understood. In this study, we investigate the efficacy of natural compounds in modulating molecular targets relevant to osteoporosis, focusing on the Mitogen-Activated Protein Kinase (MAPK) pathway and the gut microbiome's influence on bone homeostasis. Using an in silico and in vitro methodology, we have identified quercetin as a promising candidate in modulating MAPK activity, offering a potential therapeutic perspective for osteoporosis treatment.

Microbiota metabolites in bone: Shaping health and Confronting disease

The intricate interplay between the gut microbiota and bone health has become increasingly recognized as a fundamental determinant of skeletal well-being. Microbiota-derived metabolites play a crucial role in dynamic interaction, specifically in bone homeostasis. In this sense, short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, indirectly promote bone formation by regulating insulin-like growth factor-1 (IGF-1). Trimethylamine N-oxide (TMAO) has been found to increase the expression of osteoblast genes, such as Runt-related transcription factor 2 (RUNX2) and bone morphogenetic protein-2 (BMP2), thus enhancing osteogenic differentiation and bone quality through BMP/SMADs and Wnt signaling pathways. Remarkably, in the context of bone infections, the role of microbiota metabolites in immune modulation and host defense mechanisms potentially affects susceptibility to infections such as osteomyelitis. Furthermore, ongoing research elucidates the precise mechanisms through which microbiota-derived metabolites influence bone cells, such as osteoblasts and osteoclasts. Understanding the multifaceted influence of microbiota metabolites on bone, from regulating homeostasis to modulating susceptibility to infections, has the potential to revolutionize our approach to bone health and disease management. This review offers a comprehensive exploration of this evolving field, providing a holistic perspective on the impact of microbiota metabolites on bone health and diseases.

Exploring the impact of pathogenic microbiome in orthopedic diseases: machine learning and deep learning approaches

Osteoporosis, arthritis, and fractures are examples of orthopedic illnesses that not only significantly impair patients' quality of life but also complicate and raise the expense of therapy. It has been discovered in recent years that the pathophysiology of orthopedic disorders is significantly influenced by the microbiota. By employing machine learning and deep learning techniques to conduct a thorough analysis of the disease-causing microbiome, we can enhance our comprehension of the pathophysiology of many illnesses and expedite the creation of novel treatment approaches. Today's science is undergoing a revolution because to the introduction of machine learning and deep learning technologies, and the field of biomedical research is no exception. The genesis, course, and management of orthopedic disorders are significantly influenced by pathogenic microbes. Orthopedic infection diagnosis and treatment are made more difficult by the lengthy and imprecise nature of traditional microbial detection and characterization techniques. These cutting-edge analytical techniques are offering previously unheard-of insights into the intricate relationships between orthopedic health and pathogenic microbes, opening up previously unimaginable possibilities for illness diagnosis, treatment, and prevention. The goal of biomedical research has always been to improve diagnostic and treatment methods while also gaining a deeper knowledge of the processes behind the onset and development of disease. Although traditional biomedical research methodologies have demonstrated certain limits throughout time, they nevertheless rely heavily on experimental data and expertise. This is the area in which deep learning and machine learning approaches excel. The advancements in machine learning (ML) and deep learning (DL) methodologies have enabled us to examine vast quantities of data and unveil intricate connections between microorganisms and orthopedic disorders. The importance of ML and DL in detecting, categorizing, and forecasting harmful microorganisms in orthopedic infectious illnesses is reviewed in this work.

Lactobacillus plantarum 45 activates SHP2 through inhibition of oxidative stress to regulate osteoblast and osteoclast differentiation

BACKGROUND

The purpose of this study is to observe LP45 (Lactobacillus plantarum 45) to investigate the mechanism by which LP45 attenuates oxidative stress-induced damage and regulates the osteoblast-osteoclast balance.

MATERIALS AND METHODS

The oxidative stress level and osteoblast- and osteoclast-related proteins were detected by immunofluorescence staining, Western blotting, ROS fluorescent probe and ELISA. Osteoblast cell proliferation capacity was determined by the CCK-8 assay. X-ray observation and HE staining were used to detect the effect of LP45 on osteoporosis.

RESULTS

The expression level of SHP2 and Src was significantly increased, and the expression levels of NOX4, P22, P47, IL-1β, NLRP3, IRF3, RANK, β-catenin and INF-β were inhibited in LP45 group and LPS + LP45 group as compared to those in LPS group. Compared with that in LPS group, the concentration of SOD was increased and the concentration of MDA was decreased in LPS + LP45 group. The protein expressions of OPG, RANKL, RUNX3, RANK and β-catenin in LP45 group and LPS + LP45 group increased. The protein expressions of NF-κB, CREB and AP-1 in LP45 group and LPS + LP45 group decreased significantly. The results were also confirmed by immunofluorescence staining and ROS fluorescent probe. X-ray observation and HE staining showed that LP45 could inhibit the progression of osteoporosis.

CONCLUSION

LP45 can exert its antioxidant effect by inhibiting the production of oxidative stress to activate the SHP2 signaling pathway, thus promoting osteoblast differentiation and repressing osteoclast formation to maintain bone homeostasis and improve bone metabolism.

Calcium absorption by Alaska pollock surimi protein hydrolysate promotes osteoblast differentiation

The calcium-binding capacity and osteoblast proliferation and differentiation were studied in Alaska pollock surimi hydrolysate (APSH) using a system that mimics the gastrointestinal digestive system. Evaluation of the calcium absorption-promoting ability of APSH revealed that the best calcium-binding ability was achieved after hydrolysis with a combination of pepsin, α-chymotrypsin, and trypsin, and separation into <3 kDa (APSH-I), 3-5 kDa (APSH-II), 5-10 kDa (APSH-III), and <10 kDa (APSH-IV) fractions. Scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis confirmed that the hydrolysate and calcium ions formed a complex. Comparison of the calcium absorption capacity using Caco-2 cells showed that calcium absorption was promoted by these hydrolysates. Measurement of the osteoblast activation revealed higher alkaline phosphatase activity, collagen synthesis, and mineralization effect for the low-molecular-weight hydrolysate (LMH) than for the other hydrolysates. In addition, LMH promoted the expression of osteocalcin, osteopontin, and bone morphogenetic protein-2 and -4, which are hormones related to bone formation. Expression of the Runx2 transcription factor, which regulates the expression of these hormones, also increased. These results suggest that Alaska pollock surimi protein hydrolysates prepared using a system that mimics gastrointestinal hydrolysis may result in better osteoblast proliferation and bone health than those prepared using other proteases.

Gut microbially produced tryptophan metabolite melatonin ameliorates osteoporosis via modulating SCFA and TMAO metabolism

Osteoporosis (OP) is a severe global health issue that has significant implications for productivity and human lifespan. Gut microbiota dysbiosis has been demonstrated to be closely associated with OP progression. Melatonin (MLT) is an important endogenous hormone that modulates bone metabolism, maintains bone homeostasis, and improves OP progression. Multiple studies indicated that MLT participates in the regulation of intestinal microbiota and gut barrier function. However, the promising effects of gut microbiota-derived MLT in OP remain unclear. Here, we found that OP resulted in intestinal tryptophan disorder and decreased the production of gut microbiota-derived MLT, while administration with MLT could mitigate OP-related clinical symptoms and reverse gut microbiota dysbiosis, including the diversity of intestinal microbiota, the relative abundance of many probiotics such as Allobaculum and Parasutterella, and metabolic function of intestinal flora such as amino acid metabolism, nucleotide metabolism, and energy metabolism. Notably, MLT significantly increased the production of short-chain fatty acids and decreased trimethylamine N-oxide-related metabolites. Importantly, MLT could modulate the dynamic balance of M1/M2 macrophages, reduce the serum levels of pro-inflammatory cytokines, and restore gut-barrier function. Taken together, our results highlighted the important roles of gut microbially derived MLT in OP progression via the "gut-bone" axis associated with SCFA metabolism, which may provide novel insight into the development of MLT as a promising drug for treating OP.

Mechanistic study on the alleviation of postmenopausal osteoporosis by Lactobacillus acidophilus through butyrate-mediated inhibition of osteoclast activity

In China, traditional medications for osteoporosis have significant side effects, low compliance, and high costs, making it urgent to explore new treatment options. Probiotics have demonstrated superiority in the treatment of various chronic diseases, and the reduction of bone mass in postmenopausal osteoporosis (PMOP) is closely related to the degradation and metabolism of intestinal probiotics. It is crucial to explore the role and molecular mechanisms of probiotics in alleviating PMOP through their metabolites, as well as their therapeutic effects. We aim to identify key probiotics and their metabolites that affect bone loss in PMOP through 16srDNA sequencing combined with non-targeted metabolomics sequencing, and explore the impact and possible mechanisms of key probiotics and their metabolites on the progression of PMOP in the context of osteoporosis caused by estrogen deficiency. The sequencing results showed a significant decrease in Lactobacillus acidophilus and butyrate in PMOP patients. In vivo experiments confirmed that the intervention of L. acidophilus and butyrate significantly inhibited osteoclast formation and bone resorption activity, improved intestinal barrier permeability, suppressed B cells, and the production of RANKL on B cells, effectively reduced systemic bone loss induced by oophorectomy, with butyric acid levels regulated by L. acidophilus. Consistently, in vitro experiments have confirmed that butyrate can directly inhibit the formation of osteoclasts and bone resorption activity. The above research results indicate that there are various pathways through which L. acidophilus inhibits osteoclast formation and bone resorption activity through butyrate. Intervention with L. acidophilus may be a safe and promising treatment strategy for osteoclast related bone diseases, such as PMOP.

Randomized controlled trial comparing the impacts of Saccharomyces boulardii and Lactobacillus rhamnosus OF44 on intestinal flora in cerebral palsy rats: insights into inflammation biomarkers and depression-like behaviors

Background

Cerebral palsy (CP) is a unique neurological disorder which adversely affects motion. Cytokines and gut microbial composition contribute to CP and other diseases, such as reproductive tract inflammation and bone loss. Importantly, Saccharomyces boulardii (S. boulardii) reduces the degree of inflammation and improves overall health status. As our previous study showed that Lactobacillus rhamnosus (L. rhamnosus) OF44, a selected strain of gut bacteria originally used to treat reproductive tract inflammation and bone loss, has effects similar to that of S. boulardii, we decided to use L. rhamnosus OF44 on CP rats. Validation of the effects of L. rhamnosus OF44 on CP adds to its confirmed effects in treating osteoporosis and reproductive tract microbiota disorders, increasing its potential as a probiotic. The purpose of this was to ascertain whether L. rhamnosus OF44 can alleviate the symptoms of CP.

Methods

CP rat models were created through left carotid artery ligation. Following this, 100-day old CP rats were exposed to L. rhamnosus OF44, S. boulardii, or normal saline gastric gavage daily for 28 days. Grouping of the rats is determined randomly. Before and after the gavage, behavioral experiments were conducted and the inflammation levels assessed via measurements of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor alpha (TNF-α) inflammatory markers. The efficacy of the outcome is measured by performing statistical analysis like the t-test on the data to see its significance. Additionally, variations inside gut microbiome were evaluated via 16S ribosomal RNA sequencing.

Results

Before intervention, CP rats failed to exhibit depression-like behavior (P=0.6). L. rhamnosus OF44 treatment significantly reduced the level of IL-6 (P=4.8e-05), S. boulardii treatment significantly reduced the level of TNF-α (P=0.04). In addition, both treatments altered the composition and complexity of the gut microbiome.

Conclusions

Our results indicated that L. rhamnosus OF44 has potential in alleviating inflammation and altering the gut microbial composition in CP, and that it has the potential to clinically treat CP. There are some limitations of this study. For example, dietary differences and their effects on gastrointestinal dysfunction are not considered in this study, and only two behavioral experiments were used.

Global Publication Trends and Research Hotspots of the Immune System and Osteoporosis: A Bibliometric and Visualization Analysis from 2012 to 2022

BACKGROUND

Osteoporosis (OP) is a systemic bone metabolism disorder in which the immune system and bone metabolism interact.

OBJECTIVE

The purpose of this study was to explore the research status, hot spots and trends regarding the influence of the immune system on OP and to provide a basis for research directions and applications in this field.

METHODS

We searched and collected literature about the immune system and OP published from 2012 to 2022 in the Web of Science Core Collection database. All the included studies were subjected to bibliometrics analysis using Hiplot Pro, VOSviewer and CiteSpace software to produce statistics and visual analyses of the literature output, countries, institutions, authors, keywords and journals.

RESULTS

A total of 1201 papers were included, and the number of citations of these articles reached 31,776. The number of publications and citations on the immune system and OP has increased year by year. The top three countries with the greatest number of papers published were China, the United States of America (USA) and Italy. The two institutions with the largest number of papers published were Sichuan University and Soochow University, both located in China. De Martinis Massimo (Italy) and Ginaldi Lia (Italy) are prolific authors in this field. The representative academic journals are Osteoporosis International, Frontiers in Immunology, Journal of Bone and Mineral Research, PloS One and Bone. The results of the keyword cooccurrence analysis showed that the research topics in this field mainly focused on T cells, cytokines, signaling pathways, vitamin D, postmenopausal OP and immune diseases. The keyword burst results showed that zoledronic acid, chain fatty acids and gut microbiota are the frontiers and trends of future research on this topic.

CONCLUSION

The influence of the immune system on OP has been widely studied, and the current research in this field focuses on the effect or mechanism of immune-related cytokines, signaling pathways and vitamin D on OP. Future research trends in this field should focus on the immune regulation mechanism and clinical transformation of zoledronic acid, chain fatty acids and the gut microbiota in OP.

Gut-spine axis: a possible correlation between gut microbiota and spinal degenerative diseases

As society ages, the number of patients with spinal degenerative diseases (SDD) is increasing, posing a major socioeconomic problem for patients and their families. SDD refers to a generic term for degenerative diseases of spinal structures, including osteoporosis (bone), facet osteoarthritis (joint), intervertebral disk degeneration (disk), lumbar spinal canal stenosis (yellow ligament), and spinal sarcopenia (muscle). We propose the term "gut-spine axis" for the first time, given the influence of gut microbiota (GM) on the metabolic, immune, and endocrine environment in hosts through various potential mechanisms. A close cross-talk is noted between the aforementioned spinal components and degenerative diseases. This review outlines the nature and role of GM, highlighting GM abnormalities associated with the degeneration of spinal components. It also summarizes the evidence linking GM to various SDD. The gut-spine axis perspective can provide novel insights into the pathogenesis and treatment of SDD.

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.

The Impact of Tannic Acid Consumption on Bone Mineralization

Tannic acid (TA) is an organic compound belonging to the tannin group. Like other tannins, it has an affinity for endogenous proteins, including digestive enzymes, which can result in the reduced digestibility and absorption of nutrients. It can also form complexes with mineral components, reducing their absorption. In some cases, this can be beneficial, such as in the case of toxic metals, but sometimes it may have a detrimental effect on the body when it involves essential mineral components like Ca, P, Mg, Na, K, or Fe. Therefore, the impact of TA on bone health should be considered from both perspectives. This relatively short review summarizes the available information and research findings on TA, with a particular focus on its potential impact on bone health. It is worth noting that future research and clinical studies may provide more detailed and precise information on this topic, allowing for a better understanding of the role of TA in maintaining the integrity of the musculoskeletal system. Despite its brevity, this paper represents a valuable contribution to the analysis of the potential benefits and challenges associated with TA in the context of bone health. We anticipate that future research will continue along this important research line, expanding our knowledge of the influence of this compound on the skeletal system and its potential therapeutic applications.

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.

Mechanisms of action and synergetic formulas of plant-based natural compounds from traditional Chinese medicine for managing osteoporosis: a literature review

Osteoporosis (OP) is a systemic skeletal disease prevalent in older adults, characterized by substantial bone loss and deterioration of microstructure, resulting in heightened bone fragility and risk of fracture. Traditional Chinese Medicine (TCM) herbs have been widely employed in OP treatment owing to their advantages, such as good tolerance, low toxicity, high efficiency, and minimal adverse reactions. Increasing evidence also reveals that many plant-based compounds (or secondary metabolites) from these TCM formulas, such as resveratrol, naringin, and ginsenoside, have demonstrated beneficial effects in reducing the risk of OP. Nonetheless, the comprehensive roles of these natural products in OP have not been thoroughly clarified, impeding the development of synergistic formulas for optimal OP treatment. In this review, we sum up the pathological mechanisms of OP based on evidence from basic and clinical research; emphasis is placed on the in vitro and preclinical in vivo evidence-based anti-OP mechanisms of TCM formulas and their chemically active plant constituents, especially their effects on imbalanced bone homeostasis regulated by osteoblasts (responsible for bone formation), osteoclasts (responsible for bone resorption), bone marrow mesenchymal stem cells as well as bone microstructure, angiogenesis, and immune system. Furthermore, we prospectively discuss the combinatory ingredients from natural products from these TCM formulas. Our goal is to improve comprehension of the pharmacological mechanisms of TCM formulas and their chemically active constituents, which could inform the development of new strategies for managing OP.

From Cells to Environment: Exploring the Interplay between Factors Shaping Bone Health and Disease

The skeletal system is an extraordinary structure that serves multiple purposes within the body, including providing support, facilitating movement, and safeguarding vital organs. Moreover, it acts as a reservoir for essential minerals crucial for overall bodily function. The intricate interplay of bone cells plays a critical role in maintaining bone homeostasis, ensuring a delicate balance. However, various factors, both intrinsic and extrinsic, can disrupt this vital physiological process. These factors encompass genetics, aging, dietary and lifestyle choices, the gut microbiome, environmental toxins, and more. They can interfere with bone health through several mechanisms, such as hormonal imbalances, disruptions in bone turnover, direct toxicity to osteoblasts, increased osteoclast activity, immune system aging, impaired inflammatory responses, and disturbances in the gut-bone axis. As a consequence, these disturbances can give rise to a range of bone disorders. The regulation of bone's physiological functions involves an intricate network of continuous processes known as bone remodeling, which is influenced by various intrinsic and extrinsic factors within the organism. However, our understanding of the precise cellular and molecular mechanisms governing the complex interactions between environmental factors and the host elements that affect bone health is still in its nascent stages. In light of this, this comprehensive review aims to explore emerging evidence surrounding bone homeostasis, potential risk factors influencing it, and prospective therapeutic interventions for future management of bone-related disorders.

Effect of a Hop Extract Standardized in 8-Prenylnaringenin on Bone Health and Gut Microbiome in Postmenopausal Women with Osteopenia: A One-Year Randomized, Double-Blind, Placebo-Controlled Trial

Estrogen deficiency increases the risk of osteoporosis and fracture. The aim of this study was to investigate whether a hop extract standardized in 8-prenylnaringenin (8-PN), a potent phytoestrogen, could improve bone status of osteopenic women and to explore the gut microbiome roles in this effect. In this double-blind, placebo-controlled, randomized trial, 100 postmenopausal, osteopenic women were supplemented with calcium and vitamin D3 (CaD) tablets and either a hop extract (HE) standardized in 8-PN (n = 50) or a placebo (n = 50) for 48 weeks. Bone mineral density (BMD) and bone metabolism were assessed by DXA measurements and plasma bone biomarkers, respectively. Participant's quality of life (SF-36), gut microbiome composition, and short-chain fatty acid (SCFA) levels were also investigated. In addition to the CaD supplements, 48 weeks of HE supplementation increased total body BMD (1.8 ± 0.4% vs. baseline, p < 0.0001; 1.0 ± 0.6% vs. placebo, p = 0.08), with a higher proportion of women experiencing an increase ≥1% compared to placebo (odds ratio: 2.41 ± 1.07, p < 0.05). An increase in the SF-36 physical functioning score was observed with HE versus placebo (p = 0.05). Gut microbiome α-diversity and SCFA levels did not differ between groups. However, a higher abundance of genera Turicibacter and Shigella was observed in the HE group; both genera have been previously identified as associated with total body BMD. These results suggest that an 8-PN standardized hop extract could beneficially impact bone health of postmenopausal women with osteopenia.

The progress on the relationship between gut microbiota and immune checkpoint blockade in tumors

Immune checkpoint blockade (ICB) has emerged as a promising immunotherapeutic approach for the treatment of various tumors. However, the efficacy of this therapy is limited in a subset of patients, and it is important to develop strategies to enhance immune responses. Studies have demonstrated a critical role of gut microbiota in regulating the therapeutic response to ICB. Gut microbiota composition, diversity, and function are mediated by metabolites, such as short-chain fatty acids and secondary bile acids, that interact with host immune cells through specific receptors. In addition, gut bacteria may translocate to the tumor site and stimulate antitumor immune responses. Therefore, maintaining a healthy gut microbiota composition, for instance through avoiding the use of antibiotics or probiotic interventions, can be an effective approach to optimize ICB therapy. This review summarizes the current understanding of the microbiota-immunity interactions in the context of ICB therapy, and discusses potential clinical implications of these findings.

Discovery of potential biomarkers for osteoporosis diagnosis by individual omics and multi-omics technologies

INTRODUCTION

Global aging has made osteoporosis an increasingly serious public health problem. Osteoporotic fractures seriously affect the quality of life of patients and increase disability and mortality rates. Early diagnosis is important for timely intervention. The continuous development of individual- and multi-omics methods is helpful for the exploration and discovery of biomarkers for the diagnosis of osteoporosis.

AREAS COVERED

In this review, we first introduce the epidemiological status of osteoporosis and then describe the pathogenesis of osteoporosis. Furthermore, the latest progress in individual- and multi-omics technologies for exploring biomarkers for osteoporosis diagnosis is summarized. Moreover, we clarify the advantages and disadvantages of the application of osteoporosis biomarkers obtained using the omics method. Finally, we put forward valuable views on the future research direction of diagnostic biomarkers of osteoporosis.

EXPERT OPINION

Omics methods undoubtedly provide greatly contribute to the exploration of diagnostic biomarkers of osteoporosis; however, in the future, the clinical validity and clinical utility of the obtained potential biomarkers should be thoroughly examined. In addition, the improvement and optimization of the detection methods for different types of biomarkers and standardization of the detection process guarantee the reliability and accuracy of the detection results.

Beneficial effects of arketamine on the reduced bone mineral density in susceptible mice after chronic social defeat stress: Role of the gut-microbiota-bone-brain axis

Patients with depression exhibit reduced bone mineral density (BMD). We previously reported that the new antidepressant arketamine improved the reduced BMD seen in chronic social defeat stress (CSDS) susceptible mice and ovariectomized mice. Considering the role of the gut microbiota in maintaining bone health, the current study investigated whether the gut microbiota, along with metabolites derived from the microbiome, play a role in the beneficial actions of arketamine with respect to the anhedonia-like behavior and reduced BMD seen in CSDS susceptible mice. A single administration of arketamine (10 mg/kg) ameliorated anhedonia-like behavior and decreased femoral neck cortical (and total) BMD in CSDS susceptible mice. There was a negative correlation between anhedonia-like behavior and BMD. Furthermore, significant differences in the abundance of microbiota (and plasma metabolites) were found between the CSDS + saline and CSDS + arketamine groups. Correlations were observed between the abundance of certain microbiota (and plasma metabolites) and cortical (and total) BMD. These data suggest that, in addition to its anti-anhedonia effect, arketamine might ameliorate the reduced cortical (and total) BMD seen in CSDS susceptible mice through the gut-microbiota-bone-brain axis. Therefore, arketamine could serve as a drug therapy for depressed patients with low BMD. This article is part of the Special Issue on "Ketamine and its Metabolites".

Obesity, but not high-fat diet, is associated with bone loss that is reversed via CD4+CD25+Foxp3+ Tregs-mediated gut microbiome of non-obese mice

Osteoporosis is characterized by decreased bone mass, microarchitectural deterioration, and increased bone fragility. High-fat diet (HFD)-induced obesity also results in bone loss, which is associated with an imbalanced gut microbiome. However, whether HFD-induced obesity or HFD itself promotes osteoclastogenesis and consequent bone loss remains unclear. In this study, we developed HFD-induced obesity (HIO) and non-obesity (NO) mouse models to evaluate the effect of HFD on bone loss. NO mice were defined as body weight within 5% of higher or lower than that of chow diet fed mice after 10 weeks HFD feeding. NO was protected from HIO-induced bone loss by the RANKL /OPG system, with associated increases in the tibia tenacity, cortical bone mean density, bone volume of cancellous bone, and trabecular number. This led to increased bone strength and improved bone microstructure via the microbiome-short-chain fatty acids (SCFAs) regulation. Additionally, endogenous gut-SCFAs produced by the NO mice activated free fatty acid receptor 2 and inhibited histone deacetylases, resulting in the promotion of Treg cell proliferation in the HFD-fed NO mice; thereby, inhibiting osteoclastogenesis, which can be transplanted by fecal microbiome. Furthermore, T cells from NO mice retain differentiation of osteoclast precursors of RAW 264.7 macrophages ex vivo. Our data reveal that HFD is not a deleterious diet; however, the induction of obesity serves as a key trigger of bone loss that can be blocked by a NO mouse-specific gut microbiome.

Gold-nanosphere mitigates osteoporosis through regulating TMAO metabolism in a gut microbiota-dependent manner

Osteoporosis (OP) is a metabolic bone disease characterized by decreased bone mass and increased bone fragility. The imbalance of bone homeostasis modulated by osteoclasts and osteoblasts is the most crucial pathological change in osteoporosis. As a novel treatment strategy, nanomedicine has been applied in drug delivery and targeted therapy due to its high efficiency, precision, and fewer side effects. Gold nanospheres (GNS), as a common kind of gold nanoparticles (GNPs), possess significant antimicrobial and anti-inflammatory activity, which have been applied for the treatment of eye diseases and rheumatoid arthritis. However, the effect of GNS on osteoporosis remains elusive. In this study, we found that GNS significantly prevented ovariectomy (OVX)-induced osteoporosis in a gut microbiota-dependent manner. 16S rDNA gene sequencing demonstrated GNS markedly altered the gut microbial diversity and flora composition. In addition, GNS reduced the abundance of TMAO-related metabolites in OVX mice. Low TMAO levels might alleviate the bone loss phenomenon by reducing the inflammation response. Therefore, we investigated the alteration of cytokine profiles in OVX mice. GNS inhibited the release of pro-osteoclastogenic or proinflammatory cytokines including tumor necrosis factor α (TNF-α), interleukin (IL)-6, and granulocyte colony-stimulating factor (G-CSF) in the serum. In conclusion, GNS suppressed estrogen deficiency-induced bone loss by regulating the destroyed homeostasis of gut microbiota so as to reduce its relevant TMAO metabolism and restrain the release of proinflammatory cytokines. These results demonstrated the protective effects of GNS on osteoporosis as a gut microbiota modulator and offered novel insights into the regulation of the "gut-bone" axis.

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.

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.

Bifidobacterium lactis Probio-M8 improves bone metabolism in patients with postmenopausal osteoporosis, possibly by modulating the gut microbiota

PURPOSE

Postmenopausal osteoporosis (PMO) is usually managed by conventional drug treatment. However, prolonged use of these drugs cause side effects. Gut microbiota may be a potential target for treatment of PMO. This work was a three-month intervention trial aiming to evaluate the added effect of probiotics as adjunctive treatment for PMO.

METHODS

Forty patients with PMO were randomized into probiotic (n = 20; received Bifidobacterium animalis subsp. lactis Probio-M8 [Probio-M8], calcium, calcitriol) and placebo (n = 20; received placebo material, calcium, calcitriol) groups. The bone mineral density of patients was measured at month 0 (0 M; baseline) and month 3 (3 M; after three-month intervention). Blood and fecal samples were collected 0 M and 3 M. Only 15 and 12 patients from Probio-M8 and placebo groups, respectively, provided complete fecal samples for gut microbiota analysis.

RESULTS

No significant change was observed in the bone mineral density of patients at 3 M. Co-administering Probio-M8 improved the bone metabolism, reflected by an increased vitamin D3 level and decreased PTH and procalcitonin levels in serum at 3 M. Fecal metagenomic analysis revealed modest changes in the gut microbiome in both groups at 3 M. Interestingly, Probio-M8 co-administration affected the gut microbial interactive correlation network, particularly the short-chain fatty acid-producing bacteria. Probio-M8 co-administration significantly increased genes encoding some carbohydrate metabolism pathways (including ABC transporters, the phosphotransferase system, and fructose and mannose metabolism) and a choline-phosphate cytidylyltransferase.

CONCLUSIONS

Co-administering Probio-M8 with conventional drugs/supplements was more efficacious than conventional drugs/supplements alone in managing PMO. Our study shed insights into the beneficial mechanism of probiotic adjunctive treatment.

REGISTRATION NUMBER OF CLINICAL TRIAL

Chinese Clinical Trial Registry (identifier number: ChiCTR1800019268).

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.

Osteoporosis and Celiac Disease: Updates and Hidden Pitfalls

Celiac disease (CD) is an autoimmune disorder caused by gluten ingestion in genetically predisposed individuals. In addition to the typical gastrointestinal symptoms (e.g., diarrhea, bloating, and chronic abdominal pain), CD may also present with a broad spectrum of manifestations, including low bone mineral density (BMD) and osteoporosis. The etiopathology of bone lesions in CD is multifactorial and other conditions, rather than mineral and vitamin D malabsorption, may affect skeletal health, especially those related to the endocrine system. Here, we describe CD-induced osteoporosis in an attempt to enlighten new and less-known aspects, such as the influence of the intestinal microbiome and sex-related differences on bone health. This review describes the role of CD in the development of skeletal alterations to provide physicians with an updated overview on this debated topic and to improve the management of osteoporosis in CD.

Chondroitin sulfate alleviates osteoporosis caused by calcium deficiency by regulating lipid metabolism

The use of non-drug intervention for calcium deficiency has attracted attention in recent years. Although calcium carbonate is the preferred raw material for calcium supplementation, there are few reports on the mechanism of the combined action of chondroitin sulfate and calcium to alleviate osteoporosis from the perspective of gut microbiota and metabolomics. In this study, a rat model of osteoporosis was established by feeding a low-calcium diet. The intestinal microbiota abundance, fecal and plasma metabolite expression levels of rats fed a basal diet, a low-calcium diet, a low-calcium diet plus calcium carbonate, and a low-calcium diet plus chondroitin sulfate were compared. The results showed that compared with the low calcium group, the calcium content and bone mineral density of femur were significantly increased in the calcium carbonate and chondroitin sulfate groups. 16 S rRNA sequencing and metabolomics analysis showed that chondroitin sulfate intervention could reduce short-chain fatty acid synthesis of intestinal flora, slow down inflammatory response, inhibit osteoclast differentiation, promote calcium absorption and antioxidant mechanism, and alleviate osteoporosis in low-calcium feeding rats. Correlation analysis showed that the selected intestinal flora was significantly correlated with metabolites enriched in feces and plasma. This study provides scientific evidence of the potential impact of chondroitin sulfate as a dietary supplement for patients with osteoporosis.

Inferring Bacterial Community Interactions and Functionalities Associated with Osteopenia and Osteoporosis in Taiwanese Postmenopausal Women

Growing evidence suggests that the gut microbiota and their metabolites are associated with bone homeostasis and fragility. However, this association is limited to microbial taxonomic differences. This study aimed to explore whether gut bacterial community associations, composition, and functions are associated with osteopenia and osteoporosis. We compared the gut bacterial community composition and interactions of healthy postmenopausal women with normal bone density (n = 8) with those of postmenopausal women with osteopenia (n = 18) and osteoporosis (n = 21) through 16S rRNA sequencing coupled with network biology and statistical analyses. The results of this study showed reduced alpha diversity in patients with osteoporosis, followed by that in patients with osteopenia, then in healthy controls. Taxonomic analysis revealed that significantly enriched bacterial genera with higher abundance was observed in patients with osteoporosis and osteopenia than in healthy subjects. Additionally, a co-occurrence network revealed that, compared to healthy controls, bacterial interactions were higher in patients with osteoporosis, followed by those with osteopenia. Further, NetShift analysis showed that a higher number of bacteria drove changes in the microbial community structure of patients with osteoporosis than osteopenia. Correlation analysis revealed that most of these driver bacteria had a significant positive relationship with several significant metabolic pathways. Further, ordination analysis revealed that height and T-score were the primary variables influencing the gut microbial community structure. Taken together, this study evaluated that microbial community interaction is more important than the taxonomic differences in knowing the critical role of gut microbiota in postmenopausal women associated with osteopenia and osteoporosis. Additionally, the significantly enriched bacteria and functional pathways might be potential biomarkers for the prognosis and treatment of postmenopausal women with osteopenia and osteoporosis.

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.

Mitochondrial quality control and its role in osteoporosis

Mitochondria are important organelles that provide cellular energy and play a vital role in cell differentiation and apoptosis. Osteoporosis is a chronic metabolic bone disease mainly caused by an imbalance in osteoblast and osteoclast activity. Under physiological conditions, mitochondria regulate the balance between osteogenesis and osteoclast activity and maintain bone homeostasis. Under pathological conditions, mitochondrial dysfunction alters this balance; this disruption is important in the pathogenesis of osteoporosis. Because of the role of mitochondrial dysfunction in osteoporosis, mitochondrial function can be targeted therapeutically in osteoporosis-related diseases. This article reviews different aspects of the pathological mechanism of mitochondrial dysfunction in osteoporosis, including mitochondrial fusion and fission, mitochondrial biogenesis, and mitophagy, and highlights targeted therapy of mitochondria in osteoporosis (diabetes induced osteoporosis and postmenopausal osteoporosis) to provide novel targets and prevention strategies for the prevention and treatment of osteoporosis and other chronic bone diseases.

Metabolomic patterns, redox-related genes and metals, and bone fragility endpoints in the Hortega Study

BACKGROUND

The potential joint influence of metabolites on bone fragility has been rarely evaluated. We assessed the association of plasma metabolic patterns with bone fragility endpoints (primarily, incident osteoporosis-related bone fractures, and, secondarily, bone mineral density BMD) in the Hortega Study participants. Redox balance plays a key role in bone metabolism. We also assessed differential associations in participant subgroups by redox-related metal exposure levels and candidate genetic variants.

MATERIAL AND METHODS

In 467 participants older than 50 years from the Hortega Study, a representative sample from a region in Spain, we estimated metabolic principal components (mPC) for 54 plasma metabolites from NMR-spectrometry. Metals biomarkers were measured in plasma by AAS and in urine by HPLC-ICPMS. Redox-related SNPs (N = 341) were measured by oligo-ligation assay.

RESULTS

The prospective association with incident bone fractures was inverse for mPC1 (non-essential and essential amino acids, including branched-chain, and bacterial co-metabolites, including isobutyrate, trimethylamines and phenylpropionate, versus fatty acids and VLDL) and mPC4 (HDL), but positive for mPC2 (essential amino acids, including aromatic, and bacterial co-metabolites, including isopropanol and methanol). Findings from BMD models were consistent. Participants with decreased selenium and increased antimony, arsenic and, suggestively, cadmium exposures showed higher mPC2-associated bone fractures risk. Genetic variants annotated to 19 genes, with the strongest evidence for NCF4, NOX4 and XDH, showed differential metabolic-related bone fractures risk.

CONCLUSIONS

Metabolic patterns reflecting amino acids, microbiota co-metabolism and lipid metabolism were associated with bone fragility endpoints. Carriers of redox-related variants may benefit from metabolic interventions to prevent the consequences of bone fragility depending on their antimony, arsenic, selenium, and, possibly, cadmium, exposure levels.