FOS/GOS attenuates high-fat diet induced bone loss via reversing microbiota dysbiosis, high intestinal permeability and systemic inflammation in mice

Obesity induced caveolin-1 impairs osteogenesis via activating mitophagy and inhibiting Sirt1 signaling

Obesity has become a major global health problem and the effect on bone formation has received increasing attention. However, the interaction between obesity and bone metabolism is complex and still not fully understood. Here, we show that caveolin-1 (Cav1), a membrane scaffold protein involved in regulating a variety of cellular processes, plays a key regulatory role as a bridge connecting obesity and bone metabolism. High-fat diet (HFD)-induced obese C57BL/6J mouse displayed a significant increase in Cav1 expression and lower osteogenic activity; In vitro treatment of osteoblastic MC3T3-E1 cells with 1 mM free fatty acids (FFA) significantly promoted Cav1 expression and PINK1/Parkin regulated mitophagy, but inhibited the expression of osteogenic marker genes. Conversely, reduced expression of the Cav1 gene prevented these effects. Both endogenous oxidative stress and Sirt1 pathway were also significantly reduced after Cav1 knockdown in FFA-treated cells. Finally, Cav1-Sirt1 docking and co-immunoprecipitation results showed that Cav1 interacted with Sirt1 and FFA enhanced the interaction. Taken together, these results suggest that obesity impairs bone development and formation through up-regulation of the Cav1 gene, which lead to inhibition of Sirt1/FOXO1 and Sirt1/PGC-1α signaling pathways through interacting with Sirt1 molecule, and an increase of mitophagy level.

Effect of Lacticaseibacillus paracasei K56 with galactooligosaccharide synbiotics on obese individuals: an in vitro fermentation model

BACKGROUND

The use of synbiotics is emerging as a promising intervention strategy for regulating the gut microbiota and for preventing or reducing obesity, in comparison with the use of probiotics or prebiotics alone. A previous in vivo study revealed that Lacticaseibacillus paracasei K56 (L. paracasei K56) could alleviate obesity induced in high-fat-diet mice; however, the effect of the synbiotic combination of L. paracasei K56 and prebiotics in obese individuals has not been explored fully.

RESULTS

The effect of prebiotics on the proliferation of L. paracasei K56 was determined by spectrophotometry. The results showed that polydextrose (PG), xylooligosaccharide (XOS), and galactooligosaccharide (GOS) had a greater potential to be used as substrates for L. paracasei K56 than three other prebiotics (melitose, stachyose, and mannan-oligosaccharide). An in vitro fermentation model based on the feces of ten obese female volunteers was then established. The results revealed that K56_GOS showed a significant increase in GOS degradation rate and short-chain fatty acid (SCFA) content, and a decrease in gas levels, compared with PG, XOS, GOS, K56_PG, and K56_XOS. Changes in these microbial biomarkers, including a significant increase in Bacteroidota, Bifidobacterium, Lactobacillus, Faecalibacterium, and Blautia and a decrease in the Firmicutes/Bacteroidota ratio and Escherichia-Shigella in the K56_GOS group, were associated with increased SCFA content and decreased gas levels.

CONCLUSION

This study demonstrates the effect of the synbiotic combination of L. paracasei K56 and GOS on obese individuals and indicates its potential therapeutic role in obesity treatment. © 2024 Society of Chemical Industry.

TNF compromises intestinal bile-acid tolerance dictating colitis progression and limited infliximab response

The intestine constantly encounters and adapts to the external environment shaped by diverse dietary nutrients. However, whether and how gut adaptability to dietary challenges is compromised in ulcerative colitis is incompletely understood. Here, we show that a transient high-fat diet exacerbates colitis owing to inflammation-compromised bile acid tolerance. Mechanistically, excessive tumor necrosis factor (TNF) produced at the onset of colitis interferes with bile-acid detoxification through the receptor-interacting serine/threonine-protein kinase 1/extracellular signal-regulated kinase pathway in intestinal epithelial cells, leading to bile acid overload in the endoplasmic reticulum and consequent apoptosis. In line with the synergy of bile acids and TNF in promoting gut epithelial damage, high intestinal bile acids correlate with poor infliximab response, and bile acid clearance improves infliximab efficacy in experimental colitis. This study identifies bile acids as an "opportunistic pathogenic factor" in the gut that would represent a promising target and stratification criterion for ulcerative colitis prevention/therapy.

Endurance exercise associated with a fructooligosaccharide diet modulates gut microbiota and increases colon absorptive area

BACKGROUND AND AIM

Fructooligosaccharide (FOS) supplementation can stimulate beneficial intestinal bacteria growth, but little is known about its influence on training performance. Therefore, this study analyzed FOS and exercise effects on gut microbiota and intestinal morphology of C57Bl/6 mice.

METHODS

Forty male mice were divided into four groups: standard diet-sedentary (SDS), standard diet-exercised (SDE), FOS supplemented (7.5% FOS)-sedentary (FDS), and FOS supplemented-exercised (FDE), n = 10 each group. Exercise training consisted of 60 min/day, 3 days/week, for 12 weeks.

RESULTS

SDE and FDE groups had an increase in aerobic performance compared to the pretraining period and SDS and FDS groups (P < 0.01), respectively. Groups with FOS increased colonic crypts size (P < 0.05). The FDE group presented rich microbiota (α-diversity) compared to other groups. The FDE group also acquired a greater microbial abundance (β-diversity) than other groups. The FDE group had a decrease in the Ruminococcaceae (P < 0.002) and an increase in Roseburia (P < 0.003), Enterorhabdus (P < 0.004) and Anaerotruncus (P < 0.006).

CONCLUSIONS

These findings suggest that aerobic exercise associated with FOS supplementation modulates gut microbiota and can increase colonic crypt size without improving endurance exercise performance.

Diet-Induced Gut Dysbiosis and Leaky Gut Syndrome

Chronic gut inflammation promotes the development of metabolic diseases such as obesity. There is growing evidence which suggests that dysbiosis in gut microbiota and metabolites disrupt the integrity of the intestinal barrier and significantly impact the level of inflammation in various tissues, including the liver and adipose tissues. Moreover, dietary sources are connected to the development of leaky gut syndrome through their interaction with the gut microbiota. This review examines the effects of these factors on intestinal microorganisms and the communication pathways between the gut-liver and gut-brain axis. The consumption of diets rich in fats and carbohydrates has been found to weaken the adherence of tight junction proteins in the gastrointestinal tract. Consequently, this allows endotoxins, such as lipopolysaccharides produced by detrimental bacteria, to permeate through portal veins, leading to metabolic endotoxemia and alterations in the gut microbiome composition with reduced production of metabolites, such as short-chain fatty acids. However, the precise correlation between gut microbiota and alternative sweeteners remains uncertain, necessitating further investigation. This study highlights the significance of exploring the impact of diet on gut microbiota and the underlying mechanisms in the gut-liver and gut-brain axis. Nevertheless, limited research on the gut-liver axis poses challenges in comprehending the intricate connections between diet and the gut-brain axis. This underscores the need for comprehensive studies to elucidate the intricate gut-brain mechanisms underlying intestinal health and microbiota.

Nutritional therapy bridges the critical cut-off point for the closed-loop role of type 2 diabetes and bone homeostasis: A narrative review

Currently, osteoporosis-related fractures become the most cutting-edge problem of diabetes-related complications. Rational diet is not only the basis of glycemic management in type 2 diabetes patients, but also the direction of diabetic bone health. This review highlights the importance of micronutrient supplementation (including calcium, magnesium, zinc, vitamin D, vitamin K, and vitamin C) for patients with T2DM, as well as describing the constructive intermediary role of gut flora between T2DM and bone through nutrients predominantly high in dietary fiber. In addition, it is recommended to combine the Mediterranean dietary pattern with other diversified management approaches to prevent OP. Therefore, this provides a theoretical basis for the potential role of islet β-cells in promoting bone health.

Prebiotics modulate the microbiota-gut-brain axis and ameliorate anxiety and depression-like behavior in HFD-fed mice

Previous research has demonstrated that Prebiotics can influence the composition of the gut microbiota, consequently impacting mood regulation. This study aimed to assess the effects of Prebiotics, specifically Fructooligosaccharides (FOS) and Galactooligosaccharides (GOS) on neuroinflammation, depression, and anxiety-like behavior in a mouse model fed a high-fat diet (HFD). Initially, mice were divided into two groups: a control group on a standard diet (n = 15) and a group on an HFD for 18 weeks (n = 45). By the 13th week, the HFD group was further divided into experimental groups: Control (n = 15), HFD (n = 15), HFD receiving Prebiotics (n = 15), and HFD receiving Fluoxetine (n = 15). From the 13th week onward, the HFD + Prebiotics group received both the high-fat diet and a combination of FOS and GOS, while the HFD + Fluoxetine group received Fluoxetine in their drinking water. In the 18th week, all mice underwent tests to evaluate behavior, including the Tail Suspension Test (TST), Forced Swimming Test (FST), Sucrose Preference Test (SPT), and the Plus Maze Test (PMT), after which they were euthanized. Mice on the HFD exhibited increased body weight, abdominal size, blood glucose, triglyceride levels, cholesterol, insulin, HOMA index, and higher serum IL-1β. These obese mice also displayed an increased number of microglia and astrocytes, activation of the TLR4 pathway, and elevated levels of neuroinflammatory markers like TNF-α, IL-1β, and COX-2. Moreover, obese mice showed increased activation of the IDO pathway and decreased levels of NMDA receptors. Additionally, markers of neurogenesis and synaptic plasticity, such as PSD, SAP 102, CREB-p, and BDNF, were lower. Treatment with FOS and GOS reversed symptoms of depression and anxiety in mice subjected to HD. This improvement in behavior resulted from a reduction in dysbiosis with an increase in acetate-producing bacteria (B. acidifaciens and B. dorei) and intestinal permeability, leading to a decrease in chronic peripheral and central inflammation. Furthermore, the modulation of the gut-brain axis by FOS and GOS promoted elevated acetate and GPR43 levels in the brain and a reduction in the levels of pro-inflammatory cytokines, positively impacting signaling pathways of neuronal proliferation and survival in the hippocampus and prefrontal cortex.

The potential of short-chain fatty acid epigenetic regulation in chronic low-grade inflammation and obesity

Obesity and chronic low-grade inflammation, often occurring together, significantly contribute to severe metabolic and inflammatory conditions like type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. A key player is elevated levels of gut dysbiosis-associated lipopolysaccharide (LPS), which disrupts metabolic and immune signaling leading to metabolic endotoxemia, while short-chain fatty acids (SCFAs) beneficially regulate these processes during homeostasis. SCFAs not only safeguard the gut barrier but also exert metabolic and immunomodulatory effects via G protein-coupled receptor binding and epigenetic regulation. SCFAs are emerging as potential agents to counteract dysbiosis-induced epigenetic changes, specifically targeting metabolic and inflammatory genes through DNA methylation, histone acetylation, microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). To assess whether SCFAs can effectively interrupt the detrimental cascade of obesity and inflammation, this review aims to provide a comprehensive overview of the current evidence for their clinical application. The review emphasizes factors influencing SCFA production, the intricate connections between metabolism, the immune system, and the gut microbiome, and the epigenetic mechanisms regulated by SCFAs that impact metabolism and the immune system.

Prevention and Co-Management of Breast Cancer-Related Osteoporosis Using Resveratrol

Breast cancer (BC) is currently one of the most common cancers in women worldwide with a rising tendency. Epigenetics, generally inherited variations in gene expression that occur independently of changes in DNA sequence, and their disruption could be one of the main causes of BC due to inflammatory processes often associated with different lifestyle habits. In particular, hormone therapies are often indicated for hormone-positive BC, which accounts for more than 50-80% of all BC subtypes. Although the cure rate in the early stage is more than 70%, serious negative side effects such as secondary osteoporosis (OP) due to induced estrogen deficiency and chemotherapy are increasingly reported. Approaches to the management of secondary OP in BC patients comprise adjunctive therapy with bisphosphonates, non-steroidal anti-inflammatory drugs (NSAIDs), and cortisone, which partially reduce bone resorption and musculoskeletal pain but which are not capable of stimulating the necessary intrinsic bone regeneration. Therefore, there is a great therapeutic need for novel multitarget treatment strategies for BC which hold back the risk of secondary OP. In this review, resveratrol, a multitargeting polyphenol that has been discussed as a phytoestrogen with anti-inflammatory and anti-tumor effects at the epigenetic level, is presented as a potential adjunct to both support BC therapy and prevent osteoporotic risks by positively promoting intrinsic regeneration. In this context, resveratrol is also known for its unique role as an epigenetic modifier in the regulation of essential signaling processes-both due to its catabolic effect on BC and its anabolic effect on bone tissue.

Targeting the gut microbiota-related metabolites for osteoporosis: The inextricable connection of gut-bone axis

Osteoporosis is a systemic skeletal disease characterized by decreased bone mass, destruction of bone microstructure, raised bone fragility, and enhanced risk of fractures. The correlation between gut microbiota and bone metabolism has gradually become a widespread research hotspot in recent years, and successive studies have revealed that the alterations of gut microbiota and its-related metabolites are related to the occurrence and progression of osteoporosis. Moreover, several emerging studies on the relationship between gut microbiota-related metabolites and bone metabolism are also underway, and extensive research evidence has indicated an inseparable connection between them. Combined with latest literatures and based on inextricable connection of gut-bone axis, this review is aimed to summarize the relation, potential mechanisms, application strategies, clinical application prospects, and existing challenges of gut microbiota and its-related metabolites on osteoporosis, thus updating the knowledge in this research field and providing certain reference for future researches.

An Update on Prebiotics and on Their Health Effects

Prebiotic compounds were originally defined as "a nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health"; however, a significant modulation of the definition was carried out in the consensus panel of The International Scientific Association for Probiotics and Prebiotics (ISAPP), and the last definition states that "prebiotics are substrates that are selectively utilized by host microorganisms conferring a health benefit". Health effects of prebiotics compounds attracted the interest of researchers, food companies and Regulatory Agencies, as inferred by the number of articles on Scopus for the keywords "prebiotic" and "health effects", that is ca. 2000, for the period January 2021-January 2024. Therefore, the aim of this paper is to contribute to the debate on these topics by offering an overview of existing knowledge and advances in this field. A literature search was performed for the period 2012-2023 and after the selection of the most relevant items, the attention was focused on seven conditions for which at least 8-10 different studies were found, namely colorectal cancer, neurological or psychiatric conditions, intestinal diseases, obesity, diabetes, metabolic syndrome, and immune system disorders. In addition, the analysis of the most recent articles through the software VosViewer version 1.6.20 pointed out the existence of five clusters or macro-categories, namely: (i) pathologies; (ii) metabolic condvitions; (iii) structure and use in food; (iv) immunomodulation; (v) effect on gut microbiota.

IFITM3 overexpression reverses insufficient healing benefits of small extracellular vesicles from high-fat-diet BMSCs in sepsis via the HMGB1 pathway

Bone marrow mesenchymal stem cells (BMSCs) are a promising new therapy for sepsis, a common cause of death in hospitals. However, the global epidemic of metabolic syndromes, including obesity and pre-obesity, threatens the health of the human BMSC pool. The therapeutic effects of BMSCs are primarily due to the secretion of the small extracellular vesicles containing lipids, proteins, and RNA. Accordingly, studies on BMSCs, their small extracellular vesicles, and their modifications in obese individuals are becoming increasingly important. In this study, we investigated the therapeutic potential of small extracellular vesicles (sEVs) from high-fat diet BMSCs (sEVsHFD) in sepsis-induced liver-heart axis injury. We found that sEVsHFD yielded diminished therapeutic benefits compared to sEVs from chow diet BMSCs (sEVsCD). We subsequently verified that IFITM3 significantly differed in sEVsCD and sEVsHFD, alternating in septic liver tissue, and indicating its potential as a remodeling target of sEVs. IFITM3-overexpressed high-fat-diet BMSCs (HFD-BMSCs) showed that corresponding sEVs (sEVsHFD-IFITM3) markedly ameliorated liver-heart axis injury during sepsis. Lastly, we identified the protective action mechanisms of sEVsHFD-IFITM3 in sepsis-induced organ failure and HMGB1 expression and secretion was altered in septic liver and serum while HMGB1 has been demonstrated as a critical mediator of multi-organ failure in sepsis. These findings indicate that IFITM3 overexpression regenerates the therapeutic benefit of sEVs from HFD-BMSCs in sepsis via the HMGB1 pathway.

Diets intervene osteoporosis via gut-bone axis

Osteoporosis is a systemic skeletal disease that seriously endangers the health of middle-aged and older adults. Recently, with the continuous deepening of research, an increasing number of studies have revealed gut microbiota as a potential target for osteoporosis, and the research concept of the gut-bone axis has gradually emerged. Additionally, the intake of dietary nutrients and the adoption of dietary patterns may affect the gut microbiota, and alterations in the gut microbiota might also influence the metabolic status of the host, thus adjusting bone metabolism. Based on the gut-bone axis, dietary intake can also participate in the modulation of bone metabolism by altering abundance, diversity, and composition of gut microbiota. Herein, combined with emerging literatures and relevant studies, this review is aimed to summarize the impacts of different dietary components and patterns on osteoporosis by acting on gut microbiota, as well as underlying mechanisms and proper dietary recommendations.

Beneficial effect and mechanism of natural resourced polysaccharides on regulating bone metabolism through intestinal flora: A review

Bone metabolism is an important biological process for maintaining bone health. Polysaccharides of natural origin exert beneficial effects on bone metabolism. Polysaccharide molecules often have difficulty passing through the intestinal cell membrane and are directly absorbed in the gastrointestinal tract. Therefore, polysaccharides may affect intestinal flora and play a role in disease treatment. We performed a comprehensive review of the relevant literature published from 2003 to 2023. We found that several polysaccharides from traditional Chinese medicines, including Astragalus, Achyranthes bidentata and Eucommia ulmoides, and the polysaccharides from several dietary fibers mainly composed of inulin, resistant starch, and dextran could enrich the intestinal microbiota group to regulate bone metabolism. The promotion of polysaccharide decomposition by regulating the Bacteroides phylum is particularly critical. Studies on the structure-activity relationship showed that molecular weight, glycosidic bonds, and monosaccharide composition may affect the ability of polysaccharides. The mechanism by which polysaccharides regulate intestinal flora to enhance bone metabolism may be related to the regulation of short-chain fatty acids, immunity, and hormones, involving some signaling pathways, such as TGF-β, Wnt/β-catenin, BMP/Smads, and RANKL. This paper provides a useful reference for the study of polysaccharides and suggests their potential application in the treatment of bone metabolic disorders.

Potential Effects of Akkermansia Muciniphila in Aging and Aging-Related Diseases: Current Evidence and Perspectives

Akkermansia muciniphila (A. muciniphila) is an anaerobic bacterium that widely colonizes the mucus layer of the human and animal gut. The role of this symbiotic bacterium in host metabolism, inflammation, and cancer immunotherapy has been extensively investigated over the past 20 years. Recently, a growing number of studies have revealed a link between A. muciniphila, and aging and aging-related diseases (ARDs). Research in this area is gradually shifting from correlation analysis to exploration of causal relationships. Here, we systematically reviewed the association of A. muciniphila with aging and ARDs (including vascular degeneration, neurodegenerative diseases, osteoporosis, chronic kidney disease, and type 2 diabetes). Furthermore, we summarize the potential mechanisms of action of A. muciniphila and offer perspectives for future studies.

Diet composition influences the effect of high fat diets on bone in growing male mice

The effect of diet-induced obesity on bone in rodents is variable, with bone mass increases, decreases, and no impact reported. The goal of this study was to evaluate whether the composition of obesogenic diet may influence bone independent of its effect on body weight. As proof-of-principle, we used a mouse model to compare the skeletal effects of a commonly used high fat 'Western' diet and a modified high fat diet. The modified high fat diet included ground English walnut and was isocaloric for macronutrients, but differed in fatty acid composition and contained nutrients (e.g. polyphenols) not present in the standard 'Western' diet. Eight-week-old mice were randomized into 1 of 3 dietary treatments (n = 8/group): (1) low fat control diet (LF; 10 % kcal fat); (2) high fat 'Western' diet (HF; 46 % kcal fat as soybean oil and lard); or (3) modified high fat diet supplemented with ground walnuts (HF + walnut; 46 % kcal fat as soybean oil, lard, and walnut) and maintained on their respective diets for 9 weeks. Bone response in femur was then evaluated using dual energy x-ray absorptiometry, microcomputed tomography, and histomorphometry. Consumption of both obesogenic diets resulted in increased weight gain but differed in impact on bone and bone marrow adiposity in distal femur metaphysis. Mice consuming the high fat 'Western' diet exhibited a tendency for lower cancellous bone volume fraction and connectivity density, and had lower osteoblast-lined bone perimeter (an index of bone formation) and higher bone marrow adiposity than low fat controls. Mice fed the modified high fat diet did not differ from mice fed control (low fat) diet in cancellous bone microarchitecture, or osteoblast-lined bone perimeter, and exhibited lower bone marrow adiposity compared to mice fed the 'Western' diet. This proof-of-principal study demonstrates that two obesogenic diets, similar in macronutrient distribution and induction of weight gain, can have different effects on cancellous bone in distal femur metaphysis. Because the composition of the diets used to induce obesity in rodents does not recapitulate a common human diet, our finding challenges the translatability of rodent studies evaluating the impact of diet-induced obesity on bone.

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

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

Fructooligosaccharide (FOS) and Galactooligosaccharide (GOS) Improve Neuroinflammation and Cognition By Up-regulating IRS/PI3K/AKT Signaling Pathway in Diet-induced Obese Mice

Increasing evidence has indicated that prebiotics as an alternative treatment for neuropsychiatric diseases. This study evaluated the prebiotics Fructooligosaccharides (FOS) and Galactooligosaccharides (GOS) on the modulation of neuroinflammation and cognition in an experimental model of mice high-fat diet fed. Initially, mice were distributed in the following groups: (A) control standard diet (n = 15) and (B) HFD for 18 weeks (n = 30). In the 13th week, the mice were later divided into the following experimental groups: (A) Control (n = 15); (B) HFD (n = 14); and (C) HFD + Prebiotics (n = 14). From the 13th week, the HFD + Prebiotics group received a high-fat diet and a combination of FOS and GOS. In the 18th week, all animals performed the T-maze and Barnes Maze, and were later euthanized. Biochemical and molecular analyzes were performed to assess neuroinflammation, neurogenesis, synaptic plasticity, and intestinal inflammation. Mice fed HFD had higher blood glucose, triglyceridemia, cholesterolemia, and higher serum IL-1β associated with impaired learning and memory. These obese mice also showed activation of microglia and astrocytes and significant immunoreactivity of neuroinflammatory and apoptosis markers, such as TNF-α, COX-2, and Caspase-3, in addition to lower expression of neurogenesis and synaptic plasticity markers, such as NeuN, KI-67, CREB-p, and BDNF. FOS and GOS treatment significantly improved the biochemistry profile and decreased serum IL-1β levels. Treatment with FOS and GOS also reduced TNF-α, COX-2, Caspase-3, Iba-1, and GFAP-positive cells in the dentate gyrus, decreasing neuroinflammation and neuronal death caused by chronic HFD consumption. In addition, FOS and GOS promoted synaptic plasticity by increasing NeuN, p-CREB, BDNF, and KI-67, restoring spatial learning ability and memory. Moreover, FOS and GOS on HFD modulated the insulin pathway, which was proved by up-regulating IRS/PI3K/AKT signaling pathway, followed by a decreasing Aβ plate and Tau phosphorylation. Furthermore, the prebiotic intervention reshaped the HFD-induced imbalanced gut microbiota by modulating the composition of the bacterial community, markedly increasing Bacteroidetes. In addition, prebiotics decreased intestinal inflammation and leaky gut. In conclusion, FOS and GOS significantly modulated the gut microbiota and IRS/PI3K/AKT signaling pathway, decreased neuroinflammation, and promoted neuroplasticity improving spatial learning and memory. Schematic summarizing of the pathways by FOS and GOS improves memory and learning through the gut-brain axis. FOS and GOS improve the microbial profile, reducing intestinal inflammation and leaky gut in the distal colon. Specifically, the administration of FOS and GOS decreases the expression of TLR4, TNF-α, IL-1β, and MMP9 and increases the expression of occludin and IL-10. Prebiotics inhibit neuroinflammation, neuronal apoptosis, and reactive gliosis in the hippocampus but restore synaptic plasticity, neuronal proliferation, and neurogenesis.

Effects of cholesterol-lowering probiotics on non-alcoholic fatty liver disease in FXR gene knockout mice

Background/aims

Some studies showed that probiotics could improve the composition and structure of gut microbiota. Changes in the gut microbiota may alter bile acid (BAs) composition and kinetics, improving non-alcoholic fatty liver disease (NAFLD). However, it still needs to be clarified how probiotics improve both the metabolism of BAs and NAFLD. This study aimed to reveal the regulatory mechanisms of cholesterol-lowering (CL) probiotics on NAFLD from aspects involved in BA metabolism in FXR gene knockout (FXR-/-) mice.

Methods

FXR-/- male mice were randomly divided into three groups based on different interventions for 16 weeks, including normal diet (ND), high-fat diet (HFD), and probiotic intervention in the HFD (HFD+P) group. 16s rDNA sequencing and ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) were utilized to analyze the changes in gut microbiota and fecal bile acids in mice.

Results

We found that the intervention of the CL probiotics improved liver lipid deposition and function in HFD-induced NAFLD mice by decreasing the levels of total cholesterol (TC; p = 0.002) and triglyceride (TG; p = 0.001) in serum, as well as suppressing liver inflammation, such as interleukin-1 beta (IL-1β; p = 0.002) and tumor necrosis factor-alpha (TNF-α; p < 0.0001). 16S rDNA sequencing and metabolomic analyses showed that probiotics effectively reduced the abundance of harmful gut microbiota, such as Firmicutes (p = 0.005), while concomitantly increasing the abundance of beneficial gut microbiota in NAFLD mice, such as Actinobacteriota (p = 0.378), to improve NAFLD. Compared with the ND group, consuming an HFD elevated the levels of total BAs (p = 0.0002), primary BAs (p = 0.017), and secondary BAs (p = 0.0001) in mice feces, while the intervention with probiotics significantly reduced the increase in the levels of fecal total bile acids (p = 0.013) and secondary bile acids (p = 0.017) induced by HFD.

Conclusion

The CL probiotics were found to improve liver function, restore microbiota balance, correct an abnormal change in the composition and content of fecal bile acids, and repair the damaged intestinal mucosal barrier in mice with NAFLD, ultimately ameliorating the condition. These results suggested that CL probiotics may be a promising and health-friendly treatment option for NAFLD.

The Preventive Effects of Probiotic Prevotella histicola on the Bone Loss of Mice with Ovariectomy-Mediated Osteoporosis

It has been demonstrated that the disturbance of gut microbiota (GM) is closely related to the reduction of bone mass and incidence of osteoporosis (OP). The aim of this study is to investigate whether the supplementation of Prevotella histicola (Ph) can prevent the bone loss in mice with ovariectomy (OVX)-mediated OP, and further explore relevant mechanisms. Regular (once a day for 8 consecutive weeks) and quantitative (200 µL/d) perfusion of Ph (the bacteria that orally gavaged) was conducted starting from 1 week after the construction of mice models. Bone mass and bone microstructure were detected by Micro-computed tomography (Micro-CT). Expressions of intestinal permeability, pro-inflammatory cytokines, and osteogenic and osteoclastic activities of mice were analyzed by histological staining and immunohistochemistry (IHC). 16S rRNA high throughput sequencing technique was applied to analyze the alterations of composition, abundance, and diversity of collected feces. Regular and quantitative perfusion of Ph mitigated the bone loss in mice with OVX-mediated OP. Compared with OVX + PBS group, perfusion of Ph repressed osteoclastogenesis and promoted osteogenesis, reduced release of pro-inflammatory cytokine cytokines (interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α)), and reversed expressions of tight junction proteins (zonula occludens protein 1 (ZO-1) and Occludin). Besides, the perfusion of Ph improved the composition, abundance, and diversity of GM. Collectively, this study revealed that regular and quantitative perfusion of Ph can improve the bone loss in mice with OVX-mediated OP by repairing intestinal mucosal barrier damage, optimizing intestinal permeability, inhibiting release of pro-osteoclastogenic cytokines, and improving disturbance of GM.

Rational polyelectrolyte nanoparticles endow preosteoclast-targeted siRNA transfection for anabolic therapy of osteoporosis

Targeted transfection of siRNA to preosteoclasts features the potential of anti-osteoporosis, yet challenge arises from the development of satisfied delivery vehicles. Here, we design a rational core-shell nanoparticle (NP) composed of cationic and responsive core for controlled load and release of small interfering RNA (siRNA) and compatible polyethylene glycol shell modified with alendronate for enhanced circulation and bone-targeted delivery of siRNA. The designed NPs perform well on transfection of an active siRNA (siDcstamp) that interferes Dcstamp mRNA expression, leading to impeded preosteoclast fusion and bone resorption, as well as promoted osteogenesis. In vivo results corroborate the abundant siDcstamp accumulation on bone surfaces and the enhanced trabecular bone mass volume and microstructure in treating osteoporotic OVX mice by rebalancing bone resorption, formation, and vascularization. Our study validates the hypothesis that satisfied transfection of siRNA enables preserved preosteoclasts that regulate bone resorption and formation simultaneously as potential anabolic treatment for osteoporosis.

Pivotal Role of Intestinal Microbiota and Intraluminal Metabolites for the Maintenance of Gut-Bone Physiology

Intestinal microbiota, and their mutual interactions with host tissues, are pivotal for the maintenance of organ physiology. Indeed, intraluminal signals influence adjacent and even distal tissues. Consequently, disruptions in the composition or functions of microbiota and subsequent altered host-microbiota interactions disturb the homeostasis of multiple organ systems, including the bone. Thus, gut microbiota can influence bone mass and physiology, as well as postnatal skeletal evolution. Alterations in nutrient or electrolyte absorption, metabolism, or immune functions, due to the translocation of microbial antigens or metabolites across intestinal barriers, affect bone tissues, as well. Intestinal microbiota can directly and indirectly alter bone density and bone remodeling. Intestinal dysbiosis and a subsequently disturbed gut-bone axis are characteristic for patients with inflammatory bowel disease (IBD) who suffer from various intestinal symptoms and multiple bone-related complications, such as arthritis or osteoporosis. Immune cells affecting the joints are presumably even primed in the gut. Furthermore, intestinal dysbiosis impairs hormone metabolism and electrolyte balance. On the other hand, less is known about the impact of bone metabolism on gut physiology. In this review, we summarized current knowledge of gut microbiota, metabolites and microbiota-primed immune cells in IBD and bone-related complications.

Bacterial Metabolites: A Link between Gut Microbiota and Dermatological Diseases

Dysbiosis has been identified in many dermatological conditions (e.g., psoriasis, atopic dermatitis, systemic lupus erythematosus). One of the ways by which the microbiota affect homeostasis is through microbiota-derived molecules (metabolites). There are three main groups of metabolites: short-chain fatty acids (SCFAs), tryptophan metabolites, and amine derivatives including trimethylamine N-oxide (TMAO). Each group has its own uptake and specific receptors through which these metabolites can exert their systemic function. This review provides up-to-date knowledge about the impact that these groups of gut microbiota metabolites may have in dermatological conditions. Special attention is paid to the effect of microbial metabolites on the immune system, including changes in the profile of the immune cells and cytokine disbalance, which are characteristic of several dermatological diseases, especially psoriasis and atopic dermatitis. Targeting the production of microbiota metabolites may serve as a novel therapeutic approach in several immune-mediated dermatological diseases.

Cellular and Molecular Mechanisms Associating Obesity to Bone Loss

Obesity is an alarming disease that favors the upset of other illnesses and enhances mortality. It is spreading fast worldwide may affect more than 1 billion people by 2030. The imbalance between excessive food ingestion and less energy expenditure leads to pathological adipose tissue expansion, characterized by increased production of proinflammatory mediators with harmful interferences in the whole organism. Bone tissue is one of those target tissues in obesity. Bone is a mineralized connective tissue that is constantly renewed to maintain its mechanical properties. Osteoblasts are responsible for extracellular matrix synthesis, while osteoclasts resorb damaged bone, and the osteocytes have a regulatory role in this process, releasing growth factors and other proteins. A balanced activity among these actors is necessary for healthy bone remodeling. In obesity, several mechanisms may trigger incorrect remodeling, increasing bone resorption to the detriment of bone formation rates. Thus, excessive weight gain may represent higher bone fragility and fracture risk. This review highlights recent insights on the central mechanisms related to obesity-associated abnormal bone. Publications from the last ten years have shown that the main molecular mechanisms associated with obesity and bone loss involve: proinflammatory adipokines and osteokines production, oxidative stress, non-coding RNA interference, insulin resistance, and changes in gut microbiota. The data collection unveils new targets for prevention and putative therapeutic tools against unbalancing bone metabolism during obesity.

Energy Balance and Bone Health: a Nutrient Availability Perspective

PURPOSE OF REVIEW

Obesity is highly prevalent and is associated with bone fragility and fracture. The changing nutrient availability to bone in obesity is an important facet of bone health. The goal of this article is to summarize current knowledge on the effects of carbohydrate and dietary fat availability on bone, particularly in the context of other tissues.

RECENT FINDINGS

The skeleton is a primary site for fatty acid and glucose uptake. The trafficking of carbohydrates and fats into tissues changes with weight loss and periods of weight gain. Exercise acutely influences nutrient uptake into bone and may affect nutrient partitioning to bone. Bone cells secrete hormones that signal to the brain and other tissues information about its energetic state, which may alter whole-body nutrient trafficking. There is a critical need for studies to address the changes that metabolic perturbations have on nutrient availability in bone.

Association between gut microbiota and bone metabolism: Insights from bibliometric analysis

Gut microbiota has been reported to participate in bone metabolism. However, no article has quantitatively and qualitatively analyzed this crossing field. The present study aims to analyze the current international research trends and demonstrate possible hotspots in the recent decade through bibliometrics. We screened out 938 articles meeting the standards from 2001 to 2021 in the Web of Science Core Collection database. Bibliometric analyses were performed and visualized using Excel, Citespace, and VOSviewer. Generally, the annual number of published literatures in this field shows an escalating trend. The United States has the largest number of publications, accounting for 30.4% of the total. Michigan State University and Sichuan University have the largest number of publications, while Michigan State University has the highest average number of citations at 60.00. Nutrients published 49 articles, ranking first, while the Journal of Bone and Mineral Research had the highest average number of citations at 13.36. Narayanan Parameswaran from Michigan State University, Roberto Pacifici from Emory University, and Christopher Hernandez from Cornell University were the three professors who made the largest contribution to this field. Frequency analysis showed that inflammation (148), obesity (86), and probiotics (81) are keywords with the highest focus. Moreover, keywords cluster analysis and keywords burst analysis showed that "inflammation", "obesity", and "probiotics" were the most researched topics in the field of gut microbiota and bone metabolism. Scientific publications related to gut microbiota and bone metabolism have continuously risen from 2001 to 2021. The underlying mechanism has been widely studied in the past few years, and factors affecting the alterations of the gut microbiota, as well as probiotic treatment, are emerging as new research trends.

Characteristics and osteogenic mechanism of glycosylated peptides-calcium chelate

Finding effective practical components to promote bone mineralization from the diet has become an effective method to regulate bone mass. In this study, peptides-calcium chelate derived from Crimson Snapper scales protein hydrolysates (CSPHs), and xylooligosaccharide (XOS)-peptides-calcium chelate prepared by transglutaminase (TGase) pathway, named CSPHs-Ca and XOS-CSPHs-Ca-TG, were used to explore the effects of glycosylation on their structural properties and osteogenic activity in vitro. Results showed that XOS-CSPHs-Ca-TG had better calcium phosphate crystallization inhibition activity with more unified structures than CSPHs-Ca, and could effectively maintain a stable calcium content in the gastrointestinal tract. Meanwhile, the glycosylated peptide-calcium chelate could accelerate the calcium transport efficiency in the Caco-2 cell monolayer, up to 3.54 folds of the control group. Moreover, XOS-CSPHs-Ca-TG exhibited prominent osteogenic effects by promoting the proliferation of MC3T3-E1 cells, increasing the secretion of osteogenic related factors, and accelerating the formation of intracellular mineralized nodules. RT-qPCR results further confirmed that this beneficial effect of XOS-CSPHs-Ca-TG was achieved by activating the Wnt/β-catenin signaling pathway. These results suggested that glycosylation might be a promising method for optimizing structural properties and osteogenic activity of peptide-calcium chelate.

The promotion mechanism of prebiotics for probiotics: A review

Prebiotics and probiotics play a positive role in promoting human nutrition and health. Prebiotics are compounds that cannot be digested by the host, but can be used and fermented by probiotics, so as to promote the reproduction and metabolism of intestinal probiotics for the health of body. It has been confirmed that probiotics have clinical or health care functions in preventing or controlling intestinal, respiratory, and urogenital infections, allergic reaction, inflammatory bowel disease, irritable bowel syndrome and other aspects. However, there are few systematic summaries of these types, mechanisms of action and the promotion relationship between prebiotics and probiotic. Therefore, we summarized the various types of prebiotics and probiotics, their individual action mechanisms, and the mechanism of prebiotics promoting probiotics in the intestinal tract. It is hoped this review can provide new ideas for the application of prebiotics and probiotics in the future.

How high-fat diet affects bone in mice: A systematic review and meta-analysis

High-fat diet (HFD) feeding for mice is commonly used to model obesity. However, conflicting results have been reported on the relationship between HFD and bone mass. In this systematic review and meta-analysis, we synthesized data from 80 articles to determine the alterations in cortical and trabecular bone mass of femur, tibia, and vertebrae in C57BL/6 mice after HFD. Overall, we detected decreased trabecular bone mass as well as deteriorated architecture, in femur and tibia of HFD treated mice. The vertebral trabecula was also impaired, possibly due to its reshaping into a more fragmentized pattern. In addition, pooled cortical thickness declined in femur, tibia, and vertebrae. Combined with changes in other cortical parameters, HFD could lead to a larger femoral bone marrow cavity, and a thinner and more fragile cortex. Moreover, we conducted subgroup analyses to explore the influence of mice's sex and age as well as HFD's ingredients and intervention period. Based on our data, male mice or mice aged 6-12 weeks old are relatively susceptible to HFD. HFD with > 50% of energy from fats and intervention time of 10 weeks to 5 months are more likely to induce skeletal alterations. Altogether, these findings supported HFD as an appropriate model for obesity-associated bone loss and can guide future studies.

Prebiotics enhance persistence of fermented-food associated bacteria in in vitro cultivated fecal microbial communities

It is well established that the gastrointestinal (GI) microbiota plays a major role in human health. Dietary interventions, and consumption of fermented foods that contain live microbes, in particular, are among the approaches being investigated to modulate the GI microbiota and improve health. However, the persistence of fermented food-associated bacteria (FAB) within the GI tract is typically limited by host factors that limit colonization and competition with autochthonous microbes. In this research, we examined if the addition of prebiotics, dietary substrates that are selectively metabolized by microbes to improve health, would enhance the persistence of FAB. We evaluated the persistence of bacteria from three live microbe-containing fermented foods—kefir, sausage, and sauerkraut—in fecal microbial communities from four healthy adults. Fecal communities were propagated in vitro and were inoculated with fermented food-associated microbes from kefir, sausage, or sauerkraut at ~10⁷ CFU/mL. Communities were diluted 1:100 every 24 h into fresh gut simulation medium to simulate microbial community turnover in the GI tract. We measured the persistence of Lactobacillaceae from fermented foods by quantitative PCR (qPCR) and the persistence of other FAB through 16S rRNA gene sequencing. FAB were unable to persist in vitro, reaching undetectable levels within 96 h. Addition of prebiotics, including xylooligosaccharides and a mixture of fructooligosaccharides and galactooligosaccharides enhanced the persistence of some species of FAB, but the level of persistence varied by fecal donor, fermented food, and prebiotic tested. Addition of prebiotics also increased the relative abundance of Bifidobacterium species, which most likely originated from the fecal microbiota. Collectively, our results support previous in vivo studies demonstrating the transient nature of FAB in the GI tract and indicate that consumption of prebiotics may enhance their persistence.

Inonotus hispidus Protects against Hyperlipidemia by Inhibiting Oxidative Stress and Inflammation through Nrf2/NF-κB Signaling in High Fat Diet Fed Mice

Obesity is frequently associated with dysregulated lipid metabolism and lipotoxicity. Inonotus hispidus (Bull.: Fr.) P. Karst (IH) is an edible and medicinal parasitic mushroom. In this study, after a systematic analysis of its nutritional ingredients, the regulatory effects of IH on lipid metabolism were investigated in mice fed a high-fat diet (HFD). In HFD-fed mice, IH reversed the pathological state of the liver and the three types of fat and significantly decreased the levels of low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglycerides (TG), and leptin (LEP) and increased the level of high-density liptein cholesterol (HDL-C) in serum. Meanwhile, IH ameliorated liver damage by reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST), interleukin (IL)-1β, IL-6, tumor necrosis factor-alpha (TNF-α), and plasminogen activator inhibitor-1 (PAI-1) levels in the liver and serum. Compared with HFD-fed mice, IH significantly modulated the gut microbiota, changed the relative abundances of microflora at different taxonomic levels, and regulated lipid levels. The results showed that 30 differential lipids were found. Results from Western blotting confirmed that IH regulated the nuclear factor erythroid-2 related factor 2 (Nrf2)/nuclear factor-kappa B (NF-κB) signaling pathway and oxidative stress. This study aimed to provide experimental evidence for the applicability of IH in obesity treatment.

Salivary microbiota of periodontitis aggravates bone loss in ovariectomized rats

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

New Advances in Improving Bone Health Based on Specific Gut Microbiota

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

Sodium alginate and galactooligosaccharides ameliorate metabolic disorders and alter the composition of the gut microbiota in mice with high-fat diet-induced obesity

We aimed to investigate the effects of sodium alginate (SA) and galactooligosaccharides (GOS) on the metabolism and gut microbiota of high-fat diet (HFD)-fed obese mice. GOS and SA delayed high-fat diet-induced obesity, reduced the epididymal fat and liver indices, and improved the circulating lipid profile. Low- and high-dose GOS reduced weight gain by 48.8 % and 35.3 %, and low- and high-dose SA reduced it by 37.7 % and 34.4 %, respectively. GOS and SA reduced blood glucose concentration, probably by increasing the expression of glucose transporter 4. GOS and SA increased the expression of tight junction proteins (ZO-1 and occludin), reduced the D-lactic acid (D-LA) and lipopolysaccharide concentrations, and reduced the expression of toll-like receptors, consistent with improved intestinal barrier function. GOS and SA also increased the abundance of Bacteroidota, Bifidobacterium, and Lactobacillus; and reduced that of Patescibacteria in the gut. The abundance of Parabacteroides positively correlated with the circulating low-density lipoprotein-cholesterol (LDL-C) concentration; that of Lactobacillus negatively correlated with LDL-C, D-LA, and tumor necrosis factor-α concentration; and that of Bifidobacterium positively correlated with high-density lipoprotein-cholesterol concentration, according to Spearman correlation analysis. In conclusion, SA and GOS ameliorate obesity and the associated metabolic disorders in mice, and also modulate their gut microbial composition.

Naringenin is a Potential Anabolic Treatment for Bone Loss by Modulating Osteogenesis, Osteoclastogenesis, and Macrophage Polarization

Bone undergoes constant remodeling of formation by osteoblasts and resorption by osteoclasts. In particular, macrophages have been reported to play an essential role in the regulation of bone homeostasis and regeneration. Naringenin, the predominant flavanone in citrus fruits, is reported to exert anti-inflammatory, anti-osteoclastic, and osteogenic effects. However, whether naringenin could modulate the crosstalk between macrophages and osteoblasts/osteoclasts remains to be investigated. In this study, we confirmed that naringenin enhanced osteogenesis and inhibited osteoclastogenesis directly. Naringenin promoted M2 transition and the secretion of osteogenic cytokines including IL-4, IL-10, BMP2, and TGF-β, while suppressing LPS-induced M1 polarization and the production of proinflammatory factors such as TNF-α and IL-1β. In addition, the coculture of primary bone mesenchymal stem cells (BMSCs)/bone marrow monocytes (BMMs) with macrophages showed that the naringenin-treated medium significantly enhanced osteogenic differentiation and impeded osteoclastic differentiation in both inflammatory and non-inflammatory environment. Moreover, in vivo experiments demonstrated that naringenin remarkably reversed LPS-induced bone loss and assisted the healing of calvarial defect. Taken together, naringenin serves as a potential anabolic treatment for pathological bone loss.

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

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

Hyperbaric oxygen therapy improves age induced bone dyshomeostasis in non-obese and obese conditions

AIMS

To investigate the effects of hyperbaric oxygen therapy (HBOT) on metabolic disturbance, aging and bone remodeling in D-galactose-induced aging rats with and without obesity by determining the metabolic parameters, aging and oxidative stress markers, bone turnover markers, bone microarchitecture, and bone biomechanical strength.

MATERIALS AND METHODS

Male Wistar rats were fed either a normal diet (ND; n = 18) or a HFD (n = 12) for 22 weeks. At week 13, vehicle (0.9% NaCl) was injected into ND-fed rats (NDV; n = 6), while 150 mg/kg/day of D-galactose was injected into 12 ND-fed rats (NDD) and 12 HFD-fed rats (HFDD) for 10 weeks. At week 21, rats were treated with either sham (NDVS, NDDS, or HFDDS; n = 6/ group) or HBOT (NDDH, or HFDDH; n = 6/group) for 14 days. Rats were then euthanized. Blood samples, femora, and tibiae were collected.

KEY FINDINGS

Both NDD and HFDD groups developed aging as indicated by increased AGE level, increased inflammation and oxidative stress as shown by raised serum TNF-α and MDA levels, impaired bone remodeling as indicated by an increase in levels of CTX-1, TRACP-5b, and impaired bone structure/strength, when compared with those of the NDVS group. HFD aggravated these indicators of bone dyshomeostasis in D-galactose-treated rats. HBOT restored bone remodeling and bone structure/strength in the NDD group, however HBOT ameliorated bone dyshomeostasis in the HFDD group.

SIGNIFICANCE

HBOT is a potential intervention to decrease the risk of osteoporosis and bone fracture in aging with or without obesity.

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

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

Tilapia nilotica Head Lipids Improved Bone Loss by Regulating Inflammation and Serum Metabolism Through Gut Microbiota in Ovariectomized Rats

Osteoporosis is a global health problem, and it is of great significance to replace the drugs with natural functional factors. In this study, we investigated the antiosteoporotic activity of lipids prepared from Tilapia nilotica fish head lipids (THLs) in the ovariectomized osteoporosis rats. THLs are composed of neutral lipids (NL, 77.84%), phospholipids (PL, 11.86%), and glycolipids (GL, 6.47%). There were apparent differences in the fatty acid composition of disparate components, and PL contains the most abundant Ω-3 polyunsaturated fatty acids. The results proved that THLs could improve bone microstructure, increase bone mineral density, and decrease bone resorption. To illustrate the antiosteoporotic mechanism, we analyzed the changes in gut microbial communities, proinflammation factors, serum metabolites, and metabolic pathways. Further study on gut microbiota showed that THLs significantly decreased the content of Alistipes in the gut and dramatically increased the beneficial bacteria such as Oscillospira, Roseburia, and Dubosiella. Meanwhile, proinflammation factors of serum in OVX rats decreased significantly, and metabolites were changed. Therefore, we speculated that THLs improved bone loss through reducing inflammation and changing the metabolites and metabolic pathways such as arachidonic acid metabolism and primary bile acid metabolism, etc., by altering gut microbiota. The results indicated that THLs could be a functional factor with antiosteoporotic activity.

“Osteomicrobiology”: The Nexus Between Bone and Bugs

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

Gut Microbiota and Serum Metabolic Signatures of High-Fat-Induced Bone Loss in Mice

Background

Accumulating evidence indicates that high-fat diet (HFD) is a controllable risk factor for osteoporosis, but the underlying mechanism remains to be elucidated. As a primary biological barrier for nutrient entry into the human body, the composition and function of gut microbiota (GM) can be altered rapidly by HFD, which may trigger abnormal bone metabolism. In the current study, we analyzed the signatures of GM and serum metabolomics in HFD-induced bone loss and explored the potential correlations of GM and serum metabolites on HFD-related bone loss.

Methods

We conducted a mouse model with HFD-induced bone loss through a 12-week diet intervention. Micro-CT, Osmium-μCT, and histological analyses were used to observe bone microstructure and bone marrow adipose tissue. Quantitative Real-Time PCR was applied to analyze gene expression related to osteogenesis, adipogenesis, and osteoclastogenesis. Enzyme-linked immunosorbent assay was used to measure the biochemical markers of bone turnover. 16s rDNA sequencing was employed to analyze the abundance of GM, and UHPLC-MS/MS was used to identify serum metabolites. Correlation analysis was performed to explore the relationships among bone phenotypes, GM, and the metabolome.

Results

HFD induced bone loss accompanied by bone marrow adipose tissue expansion and bone formation inhibition. In the HFD group, the relative abundance of Firmicutes was increased significantly, while Bacteroidetes, Actinobacteria, Epsilonbacteraeota, and Patescibacteria were decreased compared with the ND group. Association analysis showed that thirty-two bacterial genera were significantly related to bone volume per tissue volume (BV/TV). One hundred and forty-five serum metabolites were identified as differential metabolites associated with HFD intervention, which were significantly enriched in five pathways, such as purine metabolism, regulation of lipolysis in adipocyte and cGMP-PKG signaling pathway. Sixty-four diffiential metabolites were matched to the MS2 spectra; and ten of them were positively correlated with BV/TV and five were negatively correlated with BV/TV.

Conclusions

These findings indicated that the alternations of GM and serum metabolites were related to HFD-induced bone loss, which might provide new insights into explain the occurrence and development of HFD-related osteoporosis. The regulatory effects of GM and metabolites associated with HFD on bone homeostasis required further exploration.

The Emerging Role of Gut Microbiota in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Current Evidence and Potential Therapeutic Applications

The well-known symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) are chronic pain, cognitive dysfunction, post-exertional malaise and severe fatigue. Another class of symptoms commonly reported in the context of ME/CFS are gastrointestinal (GI) problems. These may occur due to comorbidities such as Crohn's disease or irritable bowel syndrome (IBS), or as a symptom of ME/CFS itself due to an interruption of the complex interplay between the gut microbiota (GM) and the host GI tract. An altered composition and overall decrease in diversity of GM has been observed in ME/CFS cases compared to controls. In this review, we reflect on genetics, infections, and other influences that may factor into the alterations seen in the GM of ME/CFS individuals, we discuss consequences arising from these changes, and we contemplate the therapeutic potential of treating the gut to alleviate ME/CFS symptoms holistically.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): An Overview

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic systemic disease that manifests via various symptoms such as chronic fatigue, post-exertional malaise, and cognitive impairment described as “brain fog”. These symptoms often prevent patients from keeping up their pre-disease onset lifestyle, as extended periods of physical or mental activity become almost impossible. However, the disease presents heterogeneously with varying severity across patients. Therefore, consensus criteria have been designed to provide a diagnosis based on symptoms. To date, no biomarker-based tests or diagnoses are available, since the molecular changes observed also largely differ from patient to patient. In this review, we discuss the infectious, genetic, and hormonal components that may be involved in CFS pathogenesis, we scrutinize the role of gut microbiota in disease progression, we highlight the potential of non-coding RNA (ncRNA) for the development of diagnostic tools and briefly mention the possibility of SARS-CoV-2 infection causing CFS.