Galactooligosaccharides improve mineral absorption and bone properties in growing rats through gut fermentation

Alternative biological functions of lactose: a narrative review

Lactose, commonly known as "milk sugar," offers various health benefits beyond its role as an energy source. As a precursor for essential molecules, lactose impacts calcium absorption, has low cariogenicity, affects satiety, enhances athletic performance, and potentially functions as a prebiotic for gut health. However, not all individuals can digest lactose, with a minority of the population exhibiting gastrointestinal symptoms after its consumption. The ability to digest lactose during adulthood is a genetically conferred trait known as lactase persistence, which is also likely affected by epigenetic alterations and other endogenous factors. In the present review, we highlight the multifaceted health effects of lactose, including its impact on calcium absorption, its low cariogenicity, its role in satiety control, its ability to enhance athletic performance, and its potential benefits as a prebiotic for gut health. Since these benefits are inherently dependent on lactose intake trends and the digestion capacity of populations, we also present the latest available information on the current trends in lactose consumption around the world. Overall, the gathered evidence suggests that moderate lactose consumption is recommended, as it can foster multiple lifelong health benefits.

Prebiotics as modulators of colonic calcium and magnesium uptake

Ca2+ and Mg2+ are essential nutrients, and deficiency can cause serious health problems. Thus, lack of Ca2+ and Mg2+ can lead to osteoporosis, with incidence rising both in absolute and age-specific terms, while Mg2+ deficiency is associated with type II diabetes. Prevention via vitamin D or estrogen is controversial, and the bioavailability of Ca2+ and Mg2+ from supplements is significantly lower than that from milk products. Problems are likely to increase as populations age and the number of people on vegan diets surges. Developing new therapeutic strategies requires a better understanding of the molecular mechanisms involved in absorption by intestinal epithelia. The vitamin-D dependent, active pathway for the uptake of Ca2+ from the upper small intestine involving TRPV6 is highly efficient but only accounts for about 20% of total uptake. Instead, most Ca2+ uptake is thought to occur via passive paracellular diffusion across the ileum, although sufficiently high luminal concentrations are difficult to achieve.. Interestingly, colon and caecum also have a considerable capacity for the active absorption of Ca2+ and Mg2+, the molecular mechanisms of which are unclear. Intriguingly, stimulating fermentation by prebiotics enhances colonic absorption, which can rise from ~10% to ~30% of the total. Notably, fermentation releases protons, which inhibits channels highly selective for Ca2+ and Mg2+ (TRPV6 and TRPM6/TRPM7). Conversely, the non-selective cation channel TRPV3 is stimulated by both intracellular acidification and by numerous herbal compounds. Spicy, fiber-rich food, as traditionally consumed in many cultures, might enhance the uptake of Ca2+ and Mg2+ via this pathway.

Mechanisms of gut homeostasis regulating Th17/Treg cell balance in PMOP

Postmenopausal osteoporosis (PMOP) is a metabolic bone disease driven by estrogen deficiency, primarily manifesting as reduced bone mass and heightened fracture risk. Its development is intricately linked to the balance between Th17 and Treg cells. Recent studies have highlighted the significant role of gut homeostasis in PMOP. The gut microbiota profoundly impacts bone health by modulating the host's immune system, metabolic pathways, and endocrine functions. In particular, the regulation of Th17 and Treg cell balance by gut homeostasis plays a pivotal role in the onset and progression of PMOP. Th17 cells secrete pro-inflammatory cytokines that stimulate osteoclast activity, accelerating bone resorption, while Treg cells counteract this process through anti-inflammatory mechanisms, preserving bone mass. The gut microbiota and its metabolites can influence Th17/Treg equilibrium, thereby modulating bone metabolism. Furthermore, the integrity of the gut barrier is critical for systemic immune stability, and its disruption can lead to immune dysregulation and metabolic imbalances. Thus, targeting gut homeostasis to restore Th17/Treg balance offers a novel therapeutic avenue for the prevention and treatment of PMOP.

Shifts in the microbial community and metabolome in rumen ecological niches during antler growth

Antlers are hallmark organ of deer, exhibiting a relatively high growth rate among mammals, and requiring large amounts of nutrients to meet its development. The rumen microbiota plays key roles in nutrient metabolism. However, changes in the microbiota and metabolome in the rumen during antler growth are largely unknown. We investigated rumen microbiota (liquid, solid, ventral epithelium, and dorsal epithelium) and metabolic profiles of sika deer at the early (EG), metaphase (MG) and fast growth (FG) stages. Our data showed greater concentrations of acetate and propionate in the rumens of sika deer from the MG and FG groups than in those of the EG group. However, microbial diversity decreased during antler growth, and was negatively correlated with short-chain fatty acid (SCFA) levels. Prevotella, Ruminococcus, Schaedlerella and Stenotrophomonas were the dominant bacteria in the liquid, solid, ventral epithelium, and dorsal epithelium fractions. The proportions of Stomatobaculum, Succiniclasticum, Comamonas and Anaerotruncus increased significantly in the liquid or dorsal epithelium fractions. Untargeted metabolomics analysis revealed that the metabolites also changed significantly, revealing 237 significantly different metabolites, among which the concentrations of γ-aminobutyrate and creatine increased during antler growth. Arginine and proline metabolism and alanine, aspartate and glutamate metabolism were enhanced. The co-occurrence network results showed that the associations between the rumen microbiota and metabolites different among the three groups. Our results revealed that the different rumen ecological niches were characterized by distinct microbiota compositions, and the production of SCFAs and the metabolism of specific amino acids were significantly changed during antler growth.

Gut microbiome-targeted therapies and bone health across the lifespan: a scoping review

Emerging evidence suggests that bone turnover is influenced by the gut microbiome through critical bone signaling pathways. The purpose of this scoping review is to examine prebiotic, probiotic, and synbiotic interventions on bone outcomes in humans across the lifespan. PubMed, Scopus, and EBSCOhost were searched until January 2023 to identify clinical trials examining bone mineral density (BMD) or bone mineral content (BMC) with gut microbiome interventions. Of three prebiotic interventions, one reported higher areal BMD (aBMD) in adolescents. In two studies in postmenopausal women, no changes in aBMD were observed despite decreased biomarkers of bone resorption. Probiotic interventions in perimenopausal or postmenopausal women demonstrated increased aBMD or attenuated bone loss in various bone regions. All studies observed attenuated bone loss (n = 4) or increased aBMD (n = 1). One study assessed a synbiotic intervention on aBMD and observed decreased biomarkers of bone resorption but no changes in aBMD. Results suggest potential for microbiome-targeted therapies (prebiotics, probiotics and synbiotics) to attenuate bone loss. However, changes in biomarkers of bone turnover were not always accompanied by changes in bone mineralization. Future studies should utilize longer duration interventions to investigate the influence of prebiotic, probiotic, and synbiotic interventions across diverse age, sex, and ethnic cohorts.

Bioactives in Oral Nutritional Supplementation: A Pediatric Point of View

BACKGROUND

Oral nutritional supplements (ONSs) are crucial for supporting the nutritional needs of pediatric populations, particularly those with medical conditions or dietary deficiencies. Bioactive compounds within ONSs play a pivotal role in enhancing health outcomes by exerting various physiological effects beyond basic nutrition. However, the comprehensive understanding of these bioactives in pediatric ONSs remains elusive.

OBJECTIVE

This systematic narrative review aims to critically evaluate the existing literature concerning bioactive compounds present in oral nutritional supplements from a pediatric standpoint, focusing on their types, sources, bioavailability, physiological effects, and clinical implications.

METHODS

A systematic search was conducted across the major academic databases, including PubMed, Scopus, and Web of Science, employing predefined search terms related to oral nutritional supplements, bioactives, and pediatrics. Studies published between 2013 and 2024 were considered eligible for inclusion. Data extraction and synthesis were performed according to the PRISMA guidelines.

RESULTS

The initial search yielded 558 of articles, of which 72 met the inclusion criteria. The included studies encompassed a diverse range of bioactive compounds present in pediatric ONS formulations, including, but not limited to, vitamins, minerals, amino acids, prebiotics, probiotics, and phytonutrients. These bioactives were sourced from various natural and synthetic origins and were found to exert beneficial effects on growth, development, immune function, gastrointestinal health, cognitive function, and overall well-being in pediatric populations. However, variations in bioavailability, dosing, and clinical efficacy were noted across different compounds and formulations.

CONCLUSIONS

Bioactive compounds in oral nutritional supplements offer promising avenues for addressing the unique nutritional requirements and health challenges faced by pediatric populations. However, further research is warranted to elucidate the optimal composition, dosage, and clinical applications of these bioactives in pediatric ONS formulations. A deeper understanding of these bioactive compounds and their interplay with pediatric health may pave the way for personalized and effective nutritional interventions in pediatric clinical practice.

Effect of Lycium barbarum polysaccharide on osteoblast proliferation and differentiation in postmenopausal osteoporosis

OBJECTIVE

We aimed to investigate the effect of Lycium barbarum polysaccharide (LBP) on the proliferation and differentiation of osteoblasts in postmenopausal individuals with osteoporosis using in vitro cell experiments.

METHODS

We assessed the effect of long-term LBP consumption on the intestinal metabolites of individuals using a simulation of the human intestinal microbiota ecosystem. We also tested the capacity of LBP in proliferating MC3T3-E1 cells using the cell counting kit-8 (CCK-8) method and analyzed the effect of intestinal metabolites on the osteogenic differentiation of MC3T3-E1 cells by testing bone metabolism viability with relevant indicators.

RESULTS

The level of short-chain fatty acids (SCFAs) significantly increased (p < 0.05), and the concentrations of acetic acid, propionic acid, and butyric acid all showed an upward trend after the treatment using LBP. At appropriate concentrations, the fermentation supernatant can enhance osteoblast proliferation by significantly increasing the active expression of bone-alkaline phosphatase (B-ALP) and osteocalcin (OCN) in osteoblasts (p < 0.05).

CONCLUSION

By modulating the metabolites of intestinal microbiota, production of SCFAs, the prebiotic properties of LBP can enhance osteoblast differentiation through in vitro simulation experiment and cell-based assay.

The Improvement and Related Mechanism of Microecologics on the Sports Performance and Post-Exercise Recovery of Athletes: A Narrative Review

The diversity and functionality of gut microbiota may play a crucial role in the function of human motor-related systems. In addition to traditional nutritional supplements, there is growing interest in microecologics due to their potential to enhance sports performance and facilitate post-exercise recovery by modulating the gut microecological environment. However, there is a lack of relevant reviews on this topic. This review provides a comprehensive overview of studies investigating the effects of various types of microecologics, such as probiotics, prebiotics, synbiotics, and postbiotics, on enhancing sports performance and facilitating post-exercise recovery by regulating energy metabolism, mitigating oxidative-stress-induced damage, modulating immune responses, and attenuating bone loss. Although further investigations are warranted to elucidate the underlying mechanisms through which microecologics exert their effects. In summary, this study aims to provide scientific evidence for the future development of microecologics in athletics.

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

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

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.

A review of mathematical modeling of bone remodeling from a systems biology perspective

Bone remodeling is an essential, delicately balanced physiological process of coordinated activity of bone cells that remove and deposit new bone tissue in the adult skeleton. Due to the complex nature of this process, many mathematical models of bone remodeling have been developed. Each of these models has unique features, but they have underlying patterns. In this review, the authors highlight the important aspects frequently found in mathematical models for bone remodeling and discuss how and why these aspects are included when considering the physiology of the bone basic multicellular unit, which is the term used for the collection of cells responsible for bone remodeling. The review also emphasizes the view of bone remodeling from a systems biology perspective. Understanding the systemic mechanisms involved in remodeling will help provide information on bone pathology associated with aging, endocrine disorders, cancers, and inflammatory conditions and enhance systems pharmacology. Furthermore, some features of the bone remodeling cycle and interactions with other organ systems that have not yet been modeled mathematically are discussed as promising future directions in the field.

Gram-scale chemical synthesis of galactosyllactoses and their impact on infant gut microbiota in vitro

Galactooligosaccharides (GOS) are widely used as a supplement in infant nutrition to mimic the beneficial effects found in prebiotic human milk oligosaccharides (HMOs). However, the complexity of the GOS mixture makes it challenging to ascertain which of the GOS components contribute most to their health benefits. Galactosyllactoses (GLs) are lactose-based trisaccharides containing a β-galactopyranosyl residue at the 3'-position (3'galactosyllactose, 3'-GL), 4'-position (4'-galactosyllactose, 4'-GL), or the 6'-position (6'-galactosyllactose, 6'-GL). These GLs are of particular interest as they are present in both GOS mixtures and human milk at early stages of lactation. However, research on the potential health benefits of these individual GLs has been limited. Gram quantities are needed to assess their health benefits but these GLs are not readily available at this scale. In this study, we report the gram-scale chemical synthesis of 3'-GL, 4'-GL, and 6'-GL. All three galactosyllactoses were obtained on a gram scale in good purity from cheap and commercially available lactose. Furthermore, in vitro incubation of GLs with infant faecal microbiota demonstrates that the GLs were able to increase the abundance of Bifidobacterium and stimulate short chain fatty acid production.

Inulin Supplementation Modulates the Hepatic Transcriptome, Metabolome, and Ferritin Content in Ovariectomized Rats

SCOPE

Liver is an important metabolic organ regulating whole-body homeostasis. This study aims to investigate how prebiotic-induced changes in the metabolic activity of the gut microbiome (GM) and dietary calcium depletion modulates the hepatic metabolome and transcriptome.

METHODS AND RESULTS

The serum metabolome, liver metabolome, and transcriptome are determined on samples from ovariectomized (OVX) rats fed a control diet (Control, n = 7), a control diet supplemented with 5% w/w inulin (Inulin, n = 7), or a calcium-deficient diet (CaDef, n = 7). Inulin fortification is associated with higher serum concentrations of acetate, 3-hydroxybutyrate, and reduced concentration of dimethyl sulfone, revealing that changes in the metabolic activity of the GM are reflected in circulating metabolites. Metabolomics also reveal that the inulin-fortified diet results in lower concentrations of hepatic glutamate, serine, and hypoxanthine while transcriptomics reveal accompanying effects on the hepatic expression of ferric iron binding-related genes. Inulin fortification also induces effects on the hepatic expression of genes involved in olfactory transduction, suggesting that prebiotics regulate liver function through yet unidentified mechanisms involving olfactory receptors.

CONCLUSION

Inulin ingestion impacts hepatic gene expression and is associated with an upregulation of ferritin synthesis-related genes and liver ferritin content.

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

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

Dietary Isoquercetin Ameliorates Bone Loss via Restoration of the Gut Microbiota and Lipopolysaccharide-Triggered Inflammatory Status in Ovariectomy Mice

Osteoporosis is one of the skeletal degenerative diseases accompanied by bone loss and microstructure disruption. Given that the gut-bone signaling axis highly contributes to bone health, here, dietary isoquercetin (IQ) was shown to effectively improve postmenopausal osteoporosis (PMO) in an ovariectomy (OVX) mouse model through the modulation of the gut-bone cross-talk. An in vivo study showed that OVX induced striking disruption of the microbial community, subsequently causing gut leakage and gut barrier dysfunction. As a result, lipopolysaccharide (LPS)-triggered inflammatory cytokines released from the intestine to bone marrow were determined to be associated with bone loss in OVX mice. Long-term dietary IQ effectively improved microbial community and gut barrier function in the OVX mice and thus markedly improved bone loss and host inflammatory status by repressing the NF-κB signaling pathway. An in vitro study further revealed that IQ treatments dose-dependently inhibited LPS-induced inflammation and partly promoted the proliferation and differentiation of osteoblasts. These results provide new evidence that dietary IQ has the potential for osteoporosis treatment.

Effects of Different Galacto-Oligosaccharide Supplementation on Growth Performance, Immune Function, Serum Nutrients, and Appetite-Related Hormones in Holstein Calves

Our previous study showed that early supplementation with 10 g/(d·head) of galacto-oligosaccharides (GOS) in newborn Holstein dairy calves reduced the incidence of diarrhea and improved growth performance and mineral absorption. Since the dose of 10 g/(d·head) was the lowest by dose screening in our previous study, the present study was designed to investigate whether a lower amount of GOS has similar effects on growth performance, immune function, serum nutrients in newborn Holstein heifer calves, and to further investigate its effect on appetite-related hormones. Twenty-eight healthy newborn (1 day of age) Holstein heifers with similar average body weight (41.18 ± 1.90 kg) were randomly divided into four groups (n = 7): the control group (CON group), which received heated raw milk, and three experimental groups, which received heated raw milk supplemented with 2.5 (GOS2.5 group), 5 (GOS5 group), and 10 g/(d·head) (GOS10 group) GOS. All heifer calves were fed the same starter for 28 d. Supplementation with GOS linearly increased the final body weight, average daily gain, and feed efficiency in heifer calves (p < 0.01). Compared with the control group, the average daily gain and feed efficiency of heifer calves were significantly higher in the GOS5 and GOS10 groups than in the control group (p < 0.05). Furthermore, supplementation with GOS quadratically enhanced the starter and total average daily feed intake of the heifers (p < 0.01), especially in the GOS2.5 and GOS5 groups, (p < 0.05 vs. CON). The serum concentration of immunoglobulin A was linearly increased by GOS supplementation (p < 0.05), and the levels in the GOS5 and GOS10 groups were significantly higher than those in the CON group. Meanwhile, GOS linearly decreased serum interleukin-1β and interleukin-6 concentrations (p < 0.05). The serum concentration of triglycerides was also linearly decreased (p < 0.05), whereas total protein and blood urea nitrogen were linearly increased (p < 0.05). Supplementation with GOS linearly decreased the serum concentration of leptin (p < 0.05) but increased cholecystokinin and glucagon-like peptide-1 (p < 0.05). Increasing doses of GOS linearly improved serum calcium and copper concentrations (p < 0.01) and quadratically enhanced the concentration of magnesium, which peaked in the GOS5 group (p < 0.05). In conclusion, GOS supplementation reduced the incidence of diarrhea and improved the growth performance and immune function of Holstein heifer calves.

Bile acid metabolism regulatory network orchestrates bone homeostasis

Bile acids (BAs), synthesized in the liver and modified by the gut microbiota, have been widely appreciated not only as simple lipid emulsifiers, but also as complex metabolic regulators and momentous signaling molecules, which play prominent roles in the complex interaction among several metabolic systems. Recent studies have drawn us eyes on the diverse physiological functions of BAs, to enlarge the knowledge about the "gut-bone" axis due to the participation about the gut microbiota-derived BAs to modulate bone homeostasis at physiological and pathological stations. In this review, we have summarized the metabolic processes of BAs and highlighted the crucial roles of BAs targeting bile acid-activated receptors, promoting the proliferation and differentiation of osteoblasts (OBs), inhibiting the activity of osteoclasts (OCs), as well as reducing articular cartilage degradation, thus facilitating bone repair. In addition, we have also focused on the bidirectional effects of BA signaling networks in coordinating the dynamic balance of bone matrix and demonstrated the promising effects of BAs on the development or treatment for pathological bone diseases. In a word, further clinical applications targeting BA metabolism or modulating gut metabolome and related derivatives may be developed as effective therapeutic strategies for bone destruction diseases.

Dietary supplementation for female infertility: Recent advances in the nutritional therapy for premature ovarian insufficiency

Premature ovarian insufficiency (POI) ranks top in the reproductive disorders that may impair multiple functioning systems, reduce the quality of life and ultimately deprive patients of their fertility among women. Symptoms can be partially alleviated by present hormone replacement therapy that cannot improve conception or decrease occurrence rates of systemic complication. Nutritional dietary supplements are attracting more and more attention because of their safety, bioavailability, and efficacy for well-being. Nutrients in the daily food are composed of carbohydrates, fat and lipoprotein, protein and polypeptide, vitamins, and vegetable or fruits containing phytoestrogens. These are functional nutrients due to the proliferative, anti-inflammatory, anti-oxidant, and mitochondria-protective potential during the course of menopause. Apart from dietary nutrients, microbe-related nutritional substances, including probiotics, prebiotics and the combination-synbiotics, display high potential as well in supporting estrous cycle, ovarian viability and modulating other vital reproductive functions. The present review will discuss dietary and microbial nutrients and their roles and applications in the living body based upon animal or human research, evaluate possible effect mechanisms from molecular, cellular and tissue levels, and provide insights into nutritional therapy for prolonging reproductive lifespan in female patients.

Biological activity of galacto-oligosaccharides: A review

Galacto-oligosaccharides (GOS) are oligosaccharides formed by β-galactosidase transgalactosylation. GOS is an indigestible food component that can pass through the upper gastrointestinal tract relatively intact and ferment in the colon to produce short-chain fatty acids (SCFAs) that further regulate the body’s intestinal flora. GOS and other prebiotics are increasingly recognized as useful food tools for regulating the balance of colonic microbiota-human health. GOS performed well compared to other oligosaccharides in regulating gut microbiota, body immunity, and food function. This review summarizes the sources, classification, preparation methods, and biological activities of GOS, focusing on the introduction and summary of the effects of GOS on ulcerative colitis (UC), to gain a comprehensive understanding of the application of GOS.

Supplementation with galacto-oligosaccharides in early life persistently facilitates the microbial colonization of the rumen and promotes growth of preweaning Holstein dairy calves

We aimed to determine the effects of dietary supplementation with galacto-oligosaccharides (GOS) on the growth performance, serum parameters, and the rumen microbial colonization and fermentation of pre-weaning dairy calves. The study comprised 2 phases of 28 and 42 d, respectively. During phase 1, 24 newborn female Holstein dairy calves were randomly allocated to consume a diet supplemented with 10 g/d GOS (GOS, n = 12) or not (CON, n = 12). Thereafter, during phase 2, the GOS group was further divided into 2 groups: one that continued to consume GOS (GOSC, n = 6) and one that no longer consumed GOS (GOSS, n = 6), alongside the CON group. Galacto-oligosaccharides increased the average daily gain (ADG), body weight, feed efficiency, and serum high-density lipoprotein-cholesterol concentration of dairy calves during phase 1 (P < 0.05). Supplementation with GOS for the entire study reduced the incidence of diarrhea and increased the serum total protein and Ca concentrations (P < 0.05) compared with the CON group. The effect of GOS supplementation persisted after it was stopped because the ADG and final body weight of the GOSS group were higher than those of the CON group (P < 0.05). Furthermore, the GOSS group showed a persistently lower incidence of diarrhea and greater colonization of the rumen with probiotics, at the expense of less beneficial bacteria, which would promote ruminal fermentation and microbial protein synthesis. These findings provide a theoretical basis for the rational application of prebiotics and have important practical implications for the design of early life dietary interventions in dairy calf rearing.

Functional oligosaccharide fermentation in the gut: Improving intestinal health and its determinant factors-A review

The human intestine is characterized by an abundance of nutrients and a complex microbiota that make crucial contributions to overall health. These nutrients facilitate the adaptation of resident commensals to extreme environments and the development of a robust ecological network in host species. Long-term deprivation of microbiota-accessible carbohydrates (MACs) in the gut results in a loss of bacterial diversity, disruption of intestinal barrier function, and inflammatory diseases. Functional oligosaccharides are excellent MACs possessing important prebiotic properties for intestinal health through their fermentation in the gut. Its mechanism of action is predominantly attributed to acting as carbon sources for specific probiotics, promoting short-chain fatty acids production, and regulating the gut microbiota. In this review, we describe the source and structural characteristics of functional oligosaccharides, provide a framework for strategies to improve intestinal health by oligosaccharide fermentation and discuss structural determinants influencing the functional properties of oligosaccharides.

Gut Microbiota and Bone Diseases: A Growing Partnership

Gut microbiota is key to human health and disease. Convincing studies have demonstrated that dysbiosis in the commensal gut microbiota is associated with intestinal and extra-intestinal diseases. Recent explorations have significantly contributed to the understanding of the relationship between gut microbiota and bone diseases (osteoporosis, osteoarthritis, rheumatoid arthritis, and bone cancer). Gut microbiota and its metabolites may become associated with the development and progression of bone disorders owing to their critical role in nutrient absorption, immunomodulation, and the gut-brain-bone axis (regulation hormones). In this work, we review the recent developments addressing the effect of gut microbiota modulation on skeletal diseases and explore a feasible preventive approach and therapy for bone diseases.

The Influence of Nutrition on Intestinal Permeability and the Microbiome in Health and Disease

The leakage of the intestinal barrier and the disruption of the gut microbiome are increasingly recognized as key factors in different pathophysiological conditions, such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), chronic liver diseases, obesity, diabetes mellitus, types of cancer, and neuropsychiatric disorders. In this study, the mechanisms leading to dysbiosis and "leaky gut" are reviewed, and a short summary of the current knowledge regarding different diseases is provided. The simplest way to restore intestinal permeability and the microbiota could be ideal nutrition. Further therapeutic options are also available, such as the administration of probiotics or postbiotics or fecal microbiota transplantation.

Microbial Composition of a Traditional Fermented Wheat Preparation—Nishasta and Its Role in the Amelioration of Retinoic Acid-Induced Osteoporosis in Rats

Fermented foods have a long history of human use. The purpose of this study was to characterize the microbial composition of a traditional fermented wheat preparation—Nishasta— and to explore its effect in retinoic acid-induced osteoporosis in Wistar rats. The sample was suspended in sterile water (10% w/v), mixed thoroughly, filtered, and gradually diluted. Aliquots of dilutions were cultured in MRS (DeMan–Rogosa–Sharpe) medium, and colonies with similar morphologies were subjected to DNA extraction. The 16S rRNA gene of the isolates was amplified by polymerase chain reaction, checked by agarose gel electrophoresis, and finally identified by sequencing. Anti-osteoporosis screening of Nishasta was carried out in female Wistar rats using retinoic acid as an inducer (70 mg/kg, p.o. once a day for 14 days). Its effect on bone health parameters was determined. The bone metabolism markers such as hydroxyproline (HOP), tartrate-resistant acid phosphatase (TRACP), and alkaline phosphatase (ALP) were evaluated. The results of microbial characterization revealed the presence of ten clones of Lactobacillus plantarum in the fermented preparation with L. plantarum NF3 as the predominant strain. The average microbial count was 2.4 × 103 CFU/g. Retinoic acid administration led to a marked disorder of various bone health markers in rats. It also increased the levels of urine calcium and phosphorus, indicating increased bone destruction. Treatment with fermented wheat (at 200, 100, and 50 mg/kg doses, p.o. daily for 42 days after the induction of osteoporosis) improved bone mineral density in a dose-dependent manner. It also improved the bone microstructure and reduced the levels of ALP, TRACP, and HOP. Micro-CT revealed that it reduced trabecular separation and increased the percent bone volume, trabecular numbers, trabecular thickness, and bone mineral density in the rats. The results showed that the fermented wheat promoted bone formation and prevented bone resorption. Our findings clearly established the effectiveness of Nishasta against osteoporosis in Wistar rats that can be partly attributed to the improved gut calcium absorption and microbiota composition.

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

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

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

CONTEXT

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Relationship between Gut Microbiota and Bone Health

Gut microbiota (GM) are microorganisms that live in the host gastrointestinal tract, and their abundance varies throughout the host's life. With the development of sequencing technology, the role of GM in various diseases has been increasingly elucidated. Unlike earlier studies on orthopedic diseases, this review elucidates the correlation between GM health and bone health, and discusses the potential mechanism of GM effects on host metabolism, inflammation, and ability to induce or aggravate some common orthopedic diseases such as osteoarthritis, osteoporosis, rheumatoid arthritis, etc. Finally, the prospective methods of GM manipulation and evaluation of potential GM-targeting strategies in the diagnosis and treatment of orthopedic diseases are reviewed.

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

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

Nutritional intake and bone health

Osteoporotic or fragility fractures affect one in two women and one in five men who are older than 50. These events are associated with substantial morbidity, increased mortality, and an impaired quality of life. Recommended general measures for fragility fracture prevention include a balanced diet with an optimal protein and calcium intake and vitamin D sufficiency, together with regular weight-bearing physical exercise. In this narrative Review, we discuss the role of nutrients, foods, and dietary patterns in maintaining bone health. Much of this information comes from observational studies. Bone mineral density, microstructure-estimated bone strength, and trabecular and cortical microstructure are positively associated with total protein intake. Several studies indicate that fracture risk might be lower with a higher dietary protein intake, provided that the calcium supply is sufficient. Dairy products are a valuable source of these two nutrients. Hip fracture risk appears to be lower in consumers of dairy products, particularly fermented dairy products. Consuming less than five servings per day of fruit and vegetables is associated with a higher hip fracture risk. Adherence to a Mediterranean diet or to a prudent diet is associated with a lower fracture risk. These various nutrients and dietary patterns influence gut microbiota composition or function, or both. The conclusions of this Review emphasise the importance of a balanced diet including minerals, protein, and fruit and vegetables for bone health and in the prevention of fragility fractures.

Gut microbiota and bone metabolism

Osteoporosis is the most common metabolic skeletal disease. It is characterized by the deterioration of the skeletal microarchitecture and bone loss, leading to ostealgia, and even bone fractures. Accumulating evidence has indicated that there is an inextricable relationship between the gut microbiota (GM) and bone homeostasis involving host-microbiota crosstalk. Any perturbation of the GM can play an initiating and reinforcing role in disrupting the bone remodeling balance during the development of osteoporosis. Although the GM is known to influence bone metabolism, the mechanisms associated with these effects remain unclear. Herein, we review the current knowledge of how the GM affects bone metabolism in health and disease, summarize the correlation between pathogen-associated molecular patterns of GM structural components and bone metabolism, and discuss the potential mechanisms underlying how GM metabolites regulate bone turnover. Deciphering the complicated relationship between the GM and bone health will provide new insights into the prevention and treatment of osteoporosis.

The modulatory effect and implication of gut microbiota on osteoporosis: from the perspective of "brain-gut-bone" axis

Osteoporosis (OP) is a kind of systemic metabolic disease characterized by decreased bone mass and destruction of the bone microstructure. In recent years, it has become an expected research trend to explore the cross-linking relationship in the pathogenesis process of OP so as to develop reasonable and effective intervention strategies. With the further development of intestinal microbiology and the profound exploration of the gut microbiota (GM), it has been further revealed that the "brain-gut" axis may be a potential target for the bone, thereby affecting the occurrence and progression of OP. Hence, based on the concept of "brain-gut-bone" axis, we look forward to deeply discussing and summarizing the cross-linking relationship of OP in the next three parts, including the "brain-bone" connection, "gut-bone" connection, and "brain-gut" connection, so as to provide an emerging thought for the prevention strategies and mechanism researches of OP.

Nutritional and therapeutic approaches for protecting human gut microbiota from psychotropic treatments

Emerging evidence highlighted the essential role played by the microbiota-gut-brain axis in maintaining human homeostasis, including nutrition, immunity, and metabolism. Much recent work has linked the gut microbiota to many psychiatric and neurodegenerative disorders such as depression, schizophrenia, and Alzheimer's disease. Shared gut microbiota alterations or dysbiotic microbiota have been identified in these separate disorders relative to controls. Much attention has focused on the bidirectional interplay between the gut microbiota and the brain, establishing gut dysbiotic status as a critical factor in psychiatric disorders. Still, the antibiotic-like effect of psychotropic drugs, medications used for the treatment of these disorders, on gut microbiota is largely neglected. In this review, we summarize the current findings on the impact of psychotropics on gut microbiota and how their antimicrobial potency can trigger dysbiosis. We also discuss the potential therapeutic strategies, including probiotics, prebiotics, and fecal transplantation, to attenuate the dysbiosis related to psychotropics intake.

The microbiota-gut-bone axis and bone health

The gastrointestinal tract is colonized by trillions of microorganisms, consisting of bacteria, fungi, and viruses, known as the "second gene pool" of the human body. In recent years, the microbiota-gut-bone axis has attracted increasing attention in the field of skeletal health/disorders. The involvement of gut microbial dysbiosis in multiple bone disorders has been recognized. The gut microbiota regulates skeletal homeostasis through its effects on host metabolism, immune function, and hormonal secretion. Owing to the essential role of the gut microbiota in skeletal homeostasis, novel gut microbiota-targeting therapeutics, such as probiotics and prebiotics, have been proven effective in preventing bone loss. However, more well-controlled clinical trials are still needed to evaluate the long-term efficacy and safety of these ecologic modulators in the treatment of bone disorders.

Konjac Oligosaccharides Modulate the Gut Environment and Promote Bone Health in Calcium-Deficient Mice

This study aimed to investigate the beneficial effect of konjac oligosaccharides (KOS) on bone health in calcium-deficient mice. During the experimental period, low-calcium diet-fed mice were administered with calcium chloride to simulate daily calcium supplementation. Meanwhile, different levels of KOS intervened by adding them into the diet. After 8 weeks, the calcium balance status, bone mass parameters, and gut environment modulation were evaluated. The results showed that dietary KOS intervention alleviated the negative calcium balance, significantly promoted the trabecular number and cortical thickness, and remarkably enhanced the skeletal mechanical strength. Moreover, Pearson's correlation analysis among significantly changed gut microbiota, gut metabolites, and relevant physiological indexes showed that the microbial genera of Lactobacillus, Bifidobacterium, Mucispirillum, Alistipes, and unidentified Clostridia and gut metabolites of kynurenine and testosterone were significantly associated with increased bone mass. These findings provided a new insight into the effect of prebiotics on bone health.

Effect of Xylo-Oligosaccharides Supplementation by Drinking Water on the Bone Properties and Related Calcium Transporters in Growing Mice

Xylo-oligosaccharides (XOS), non-digestible oligosaccharides, have the potential to regulate intestinal microorganisms, and thus, improve host health, but little evidence exists for the prebiotic effects on bone health. This study evaluates the dose-response effect of XOS supplementation on bone properties, the morphology of the intestine, cecum pH, and cecum wall weight, as well as the related calcium transporters. Ninety-six 28-day-old male mice were randomized into one of four groups, fed the same commercial diet, and given different types of deionized water containing 0, 1, 2, or 4% XOS by concentration for 30 days. Eight mice were randomly selected to accomplish particular tasks every 10 days. No significant differences in serum Ca and P levels and growth performance were observed among the four studied groups. XOS intervention significantly decreased cecum pH and increased cecum wall weight in a dose-dependent manner. At the late growth stage, compared with 0% XOS, the bone mineral density (BMD) and bone-breaking strength in 4% XOS were significantly higher. The bone crystallinity with 4% XOS, measured by Raman spectrum, was significantly enhanced compared to that with 0% XOS during later growth. The villus height and villus height to crypt depth (VH:CD) were enhanced with an increase of XOS concentration during the later stage of growth. The expression of transient receptor potential vanillin receptor 6 (TRPV6) and Na⁺/Ca²⁺ exchanger 1 (NCX1) in the duodenum were enhanced by XOS supplementation. XOS exerted a positive influence on bone properties by decreasing the cecum pH, increasing the cecum wall and villus structure, and upregulating the expression of related calcium transporters.

Use of Calcium Isotopic Tracers To Determine Factors That Perturb Calcium Metabolism

Calcium plays an important role in maintaining bone health. Ensuring adequate calcium intake throughout life is essential for reaching greater peak bone mass in young adulthood and lowering osteoporotic fracture risk when aging. Calcium homeostasis involves a complex interaction between three organ systems: intestine, kidney, and bone. Metabolic balance plus kinetic studies using calcium isotopic tracers can estimate calcium metabolism parameters and pinpoint how organs and processes are perturbed by internal and external modifiers. Both modifiable factors (e.g., vitamin D supplementations and dietary bioactives) and non-modifiable factors (e.g., age, sex, and race) influence calcium utilization. Current evidence suggests that prebiotic fibers may offer an alternative approach to enhance calcium absorption through altering gut microbiota to ultimately improve bone health.

Lactobacillus Fermentum ZS40 prevents secondary osteoporosis in Wistar Rat

Using retinoic acid to inducer, we successfully established a rat model of secondary osteoporosis and verified the preventive effect of Lactobacillus fermentum ZS40 (ZS40) on secondary osteoporosis. Serum biochemical indicators showed that ZS40 can effectively slow down bone resorption caused by retinoic acid, increase blood content of calcium, phosphorus, bone alkaline phosphatase, bone gla protein, and insulin-like growth factor 1, and decrease blood content of tartrate-resistant acid phosphatase (TRAP) 5b. qRT-PCR results showed that ZS40 could upregulate mRNA expressions of β-catenin, Wnt10b, Lrp5, Lrp6, Runx2, ALP, RANKL, and OPG, and downregulate mRNA expression of DKK1, RANK, TRACP, and CTSK in the rats' spinal cord. Results following TRAP staining showed that ZS40 could slow down retinoic acid-induced formation of osteoclasts. Micro-CT results showed that ZS40 could reduce Tb.Sp, increase BV/TV, Tb.N, Tb.Th, and ultimately increase bone mineral density of rats in vivo. These findings indicate that ZS40 might have a potential role in preventing retinoic acid-induced secondary osteoporosis in vivo.

Mapping the Transglycosylation Relevant Sites of Cold-Adapted β-d-Galactosidase from Arthrobacter sp. 32cB

β-Galactosidase from Arthrobacter sp. 32cB (ArthβDG) is a cold-adapted enzyme able to catalyze hydrolysis of β-d-galactosides and transglycosylation reaction, where galactosyl moiety is being transferred onto an acceptor larger than a water molecule. Mutants of ArthβDG: D207A and E517Q were designed to determine the significance of specific residues and to enable formation of complexes with lactulose and sucrose and to shed light onto the structural basis of the transglycosylation reaction. The catalytic assays proved loss of function mutation E517 into glutamine and a significant drop of activity for mutation of D207 into alanine. Solving crystal structures of two new mutants, and new complex structures of previously presented mutant E441Q enables description of introduced changes within active site of enzyme and determining the importance of mutated residues for active site size and character. Furthermore, usage of mutants with diminished and abolished enzymatic activity enabled solving six complex structures with galactose, lactulose or sucrose bounds. As a result, not only the galactose binding sites were mapped on the enzyme's surface but also the mode of lactulose, product of transglycosylation reaction, and binding within the enzyme's active site were determined and the glucopyranose binding site in the distal of active site was discovered. The latter two especially show structural details of transglycosylation, providing valuable information that may be used for engineering of ArthβDG or other analogous galactosidases belonging to GH2 family.

Are Probiotics the New Calcium and Vitamin D for Bone Health?

PURPOSE OF REVIEW

Calcium and vitamin D supplementation is recommended for patients at high risk of fracture and/or for those receiving pharmacological osteoporosis treatments. Probiotics are micro-organisms conferring a health benefit on the host when administered in adequate amounts, likely by influencing gut microbiota (GM) composition and/or function. GM has been shown to influence various determinants of bone health.

RECENT FINDINGS

In animal models, probiotics prevent bone loss associated with estrogen deficiency, diabetes, or glucocorticoid treatments, by modulating both bone resorption by osteoclasts and bone formation by osteoblast. In humans, they interfere with 25-hydroxyvitamin D levels, and calcium intake and absorption, and slightly decrease bone loss in elderly postmenopausal women, in a quite similar magnitude as observed with calcium ± vitamin D supplements. A dietary source of probiotics is fermented dairy products which can improve calcium balance, prevent secondary hyperparathyroidism, and attenuate age-related increase of bone resorption and bone loss. Additional studies are required to determine whether probiotics or any other interventions targeting GM and its metabolites may be adjuvant treatment to calcium and vitamin D or anti-osteoporotic drugs in the general management of patients with bone fragility.

The role of gut microbiota in bone homeostasis

The gut microbiota (GM) is referred to as the second gene pool of the human body and a commensal, symbiotic, and pathogenic microorganism living in our intestines. The knowledge of the complex interaction between intestinal microbiota and health outcomes is a novel and rapidly expanding the field. Earlier studies have reported that the microbial communities affect the cellular responses and shape many aspects of physiology and pathophysiology within the body, including muscle and bone metabolism (formation and resorption). GM influences the skeletal homeostasis via affecting the host metabolism, immune function, hormone secretion, and the gut-brain axis. The premise of this review is to discuss the role of GM on bone homeostasis and skeletal muscle mass function. This review also opens up new perspectives for pathophysiological studies by establishing the presence of a 'microbiota-skeletal' axis and raising the possibility of innovative new treatments for skeletal development.

Calcium Bioavailability of Opuntia ficus-indica Cladodes in an Ovariectomized Rat Model of Postmenopausal Bone Loss

Osteoporosis is a disease of the skeletal system characterized by low bone mass and bone weakening, which increase the risk of fracture. This disease is associated with menopause because hypoestrogenism induces the maturation and activation of osteoclasts. In addition, a low dietary intake of calcium leads to low bone mineral density and postmenopausal osteoporosis. The objectives of this work were to determine calcium bioavailability of Opuntia ficus-indica cladodes at a late maturity stage and to assess its contribution in improving bone health in an ovariectomized rat model. Two-month-old Wistar female rats (n = 35) were used and distributed in seven experimental groups: (i) control group (Crtl), (ii) sham group (SH), (iii) ovariectomized group (OVX), (iv) ovariectomized group supplemented with calcium citrate (CCa), (v) ovariectomized group supplemented with O. ficus-indica powder (NI), (vi) ovariectomized group supplemented with soluble fiber from O. ficus-indica (FS) and (vii) ovariectomized group supplemented with insoluble fiber from O. ficus-indica (FI). Our results showed that calcium in the soluble fiber of O. ficus-indica is bioavailable and contributes to improve the physical, densitometric, biomechanical and microstructural properties of bones in ovariectomized rats. These findings indicated that O. ficus-indica cladodes at a late maturity stage represent a good source of bioavailable calcium and consumption of these cladodes might be beneficial for the prevention of osteoporosis and other bone diseases.

Protective effects of Bifidobacterium adolescentis on collagen-induced arthritis in rats depend on timing of administration

Emerging studies have addressed the role of probiotics in inflammation modulation via modifying gut microbiota. Perturbed gut microbiota is recognized as a pivotal trigger in the pathogenesis of rheumatoid arthritis (RA), and manipulating gut microbiota at the early phase may be helpful to alleviate the disease based on the fact that dysbiosis occurred prior to clinical arthritis. The current study compared the effects of preventive and therapeutic treatment with Bifidobacterium adolescentis on collagen induced arthritis (CIA) in rats. Early B. adolescentis administration before CIA modelling performed better than late B. adolescentis treatment in reducing the clinical symptoms, rebalancing the pro- and anti-inflammatory responses and maintaining the fecal concentration of short chain fatty acids (SCFAs), as well as restoring the intestinal dysbiosis. Preventive B. adolescentis treatment restored the gut microbiota to a normal level while late B. adolescentis fed rats showed clearly different gut microbial profiles. In addition, there were slight discrepancies between early- and late- treatment of B. adolescentis in the production of specific auto-antibodies and tight junction proteins. All those results highlighted that early treatment of probiotics in arthritis might be a better timing for alleviating arthritis.

The role of prebiotics in cognition, anxiety, and depression

The disruption of the gut microbial composition, defined as dysbiosis, has been associated with many neurological disorders with inflammatory components. The alteration of the gut microbiota leads to an increase in pro-inflammatory cytokines that are associated with metabolic diseases (such as obesity and type 2 diabetes), autoimmune arthritis, and neuropsychiatric diseases. Prebiotics are defined as non-digestible carbohydrates and promote the growth of beneficial bacteria such as bifidobacteria and lactobacillus, exert beneficial effects on improving dysbiosis and its associated inflammatory state. Preclinical and clinical data indicated that some prebiotics also have positive impacts on the central nervous system (CNS) due to the modulation of neuroinflammation and thus may have a key role in the modulation of cognitive impairment, anxiety, and depression. The present manuscript reviews the state-of-art of the effects of prebiotics in cognitive impairment, anxiety, and depressive disorders. Data from clinical studies are still scarce, and further clinical trials are needed to corroborate the potential therapeutic cognitive, antidepressant, and anxiolytic of prebiotics. Prebiotics may provide patients suffering from cognitive deficits, depression, and anxiety with a new tool to minimize disease symptoms and increase the quality of life.

Pasteurized Akkermansia muciniphila protects from fat mass gain but not from bone loss

Probiotic bacteria can protect from ovariectomy (ovx)-induced bone loss in mice. Akkermansia muciniphila is considered to have probiotic potential due to its beneficial effect on obesity and insulin resistance. The purpose of the present study was to determine if treatment with pasteurized Akkermansia muciniphila (pAkk) could prevent ovx-induced bone loss. Mice were treated with vehicle or pAkk for 4 wk, starting 3 days before ovx or sham surgery. Treatment with pAkk reduced fat mass accumulation confirming earlier findings. However, treatment with pAkk decreased trabecular and cortical bone mass in femur and vertebra of gonadal intact mice and did not protect from ovx-induced bone loss. Treatment with pAkk increased serum parathyroid hormone (PTH) levels and increased expression of the calcium transporter Trpv5 in kidney suggesting increased reabsorption of calcium in the kidneys. Serum amyloid A 3 (SAA3) can suppress bone formation and mediate the effects of PTH on bone resorption and bone loss in mice and treatment with pAkk increased serum levels of SAA3 and gene expression of Saa3 in colon. Moreover, regulatory T cells can be protective of bone and pAkk-treated mice had decreased number of regulatory T cells in mesenteric lymph nodes and bone marrow. In conclusion, treatment with pAkk protected from ovx-induced fat mass gain but not from bone loss and reduced bone mass in gonadal intact mice. Our findings with pAkk differ from some probiotics that have been shown to protect bone mass, demonstrating that not all prebiotic and probiotic factors have the same effect on bone.

The Interplay between Immune System and Microbiota in Osteoporosis

Osteoporosis is a disease characterized by low bone mass and alterations of bone microarchitecture, with an increased risk of fractures. It is a multifactorial disorder that is more frequent in postmenopausal women but can be associated to other diseases (inflammatory and metabolic diseases). At present, several options are available to treat osteoporosis trying to block bone reabsorption and reduce the risk of fracture. Anyway, these drugs have safety and tolerance problems in long-term treatment. Recently, gut microbiota has been highlighted to have strong influence on bone metabolism, becoming a potential new target to modify bone mineral density. Such evidences are mainly based on mouse models, showing an involvement in modulating the interaction between the immune system and bone cells. Germ-free mice represent a basic model to understand the interaction between microbiota, immune system, and bone cells, even though data are controversial. Anyway, such models have unequivocally demonstrated a connection between such systems, even if the mechanism is unclear. Gut microbiota is a complex system that influences calcium and vitamin D absorption and modulates gut permeability, hormonal secretion, and immune response. A key role is played by the T helper 17 lymphocytes, TNF, interleukin 17, and RANK ligand system. Other important pathways include NOD1, NOD2, and Toll-like receptor 5. Prebiotics and probiotics are a wide range of substances and germs that can influence and modify microbiota. Several studies demonstrated actions by different prebiotics and probiotics in different animals, differing according to sex, age, and hormonal status. Data on the effects on humans are poor and controversial. Gut microbiota manipulation appears a possible strategy to prevent and treat osteopenia and/or osteoporosis as well as other possible bone alterations, even though further clinical studies are necessary to identify correct procedures in humans.

The gut-bone axis: how bacterial metabolites bridge the distance

The gut microbiome is a key regulator of bone health that affects postnatal skeletal development and skeletal involution. Alterations in microbiota composition and host responses to the microbiota contribute to pathological bone loss, while changes in microbiota composition that prevent, or reverse, bone loss may be achieved by nutritional supplements with prebiotics and probiotics. One mechanism whereby microbes influence organs of the body is through the production of metabolites that diffuse from the gut into the systemic circulation. Recently, short-chain fatty acids (SCFAs), which are generated by fermentation of complex carbohydrates, have emerged as key regulatory metabolites produced by the gut microbiota. This Review will focus on the effects of SCFAs on the musculoskeletal system and discuss the mechanisms whereby SCFAs regulate bone cells.