Targeting the gut microbiome to treat the osteoarthritis of obesity

The Role of Depletion of Gut Microbiota in Osteoporosis and Osteoarthritis: A Narrative Review

Osteoporosis and osteoarthritis are common diseases in an aging society, are considered metabolic diseases, and affect the quality of life of older adults. In addition, the gut microbiome is considered an additional organ to regulate bone metabolism. In the past decade, people have been studying the relationship between gut microbiota and bone metabolism. The role and mechanism of the gut microbiota in regulating bone metabolism is very important to improve the development of osteoporosis and osteoarthritis. Depletion of the gut microbiota as a method of studying the role of the gut microbiota was provided strategies to enhance the role of the gut microbiota in regulating osteoporosis and osteoarthritis. In this review, we discuss how depletion of the gut microbiota affects osteoporosis and osteoarthritis.

Mycoplasma gallisepticum induced inflammation-mediated Th1/Th2 immune imbalance via JAK/STAT signaling pathway in chicken trachea: Involvement of respiratory microbiota

The respiratory microbiota plays a significant role in the host defense against Mycoplasma gallisepticum (MG) infection. The results showed that MG infection changed respiratory microbiota composition, which lead to the tracheal inflammation injury and oxidative stress. MG infection significantly induced immunosuppression in chickens at day 3 and 5 post-infection. In addition, MG infection increased the expressions of pro-inflammatory cytokines in tracheal tissues and activated TLR4 mediated JAK/STAT signaling pathway at day 3 post-infection compared to the control group. Meanwhile, the expressions of pro-inflammatory cytokines were decreased and the expressions of JAK/STAT signaling pathway were decreased at day 5 and day 7 post-infection. On the contrary, the expressions of anti-inflammatory cytokines were significantly decreased at day 3 post-infection and were increased at day 5 and day 7 post-infection in the MG infection group. The antibiotic cocktail group received the respiratory microbiota from the MG infection group, which induced inflammatory injury and oxidative stress, induced mucosal barrier damage by down regulating tight junction-related genes and altered the expressions of mucin, which could be the possible causes of dysregulated immune responses. Importantly, the expressions of pro-inflammatory cytokines were significantly decreased and TLR4 mediated JAK/STAT signaling pathway was downregulated at day 1 and 3 post-transplantation. While, respiratory microbiota transplanted from MG infection significantly increased the expressions of pro-inflammatory cytokines and activated JAK/STAT signaling at day 7 post-transplantation. These results highlighted the role of respiratory microbiota in MG-induced tracheal inflammation injury, and offered a new strategy for the preventive intervention of this disease.

The relation between the gut microbiome and osteoarthritis: A systematic review of literature

Background

Along with mechanical and genetic factors, emerging evidence suggests that the presence of low-grade inflammation has a role in the pathogenesis of osteoarthritis (OA) and seems to be related to the microbiome composition of the gut.

Purpose

To provide evidence whether there is clinical or preclinical evidence of gut-joint axis in the pathogenesis and symptoms of OA.

Methods

An extensive review of the current literature was performed using three different databases. Human, as well as animal studies, were included. The risk of bias was identified using ROBINS and SYRCLE tools, while the quality of evidence was assessed using GRADE and CAMADARES criteria.

Results

A total of nineteen articles were included. Multiple animal studies demonstrated that both obesity, and high-fat and high-sugar diets resulted in a gut dysbiosis status characterized by increased Firmicutes/Bacteroidetes (F/B) phyla ratio and increased permeability. These changes were associated with increased lipopolysaccharide serum levels, which consequently resulted in synovitis and OA severity. The administration of pre-and probiotics partially reversed this bacterial composition. In addition, in human studies, a decreased amount of gut Bacteroidetes, subsequent increased F/B ratio, have also been observed in OA patients.

Conclusions

Our review confirms preliminary yet sound evidence supporting a gut-joint axis in OA in primarily preclinical models, by showing an association between diet, gut dysbiosis and OA radiological severity and self-reported symptoms. Clinical studies are needed to confirm these findings, and to investigate whether interventions targeting the composition of the microbiome will have a beneficial clinical effect.

The causal role of gut microbiota in development of osteoarthritis

OBJECTIVE

There is considerable evidence for relationship between gut microbiota and osteoarthritis (OA), but no studies have investigated their causal relationship.

METHOD

This study utilized large-scale genome-wide association studies (GWAS) summary statistics to evaluate the causal association between gut microbiota and OA risk. Specifically, two-sample Mendelian randomization (MR) approach was used to identify the causal microbial taxa for OA. Comprehensively sensitive analyses were performed to validate the robustness of results and novel multivariable MR analyses were further conducted to ensure the independence of causal association. Reverse-direction MR analyses were performed to rule out the possibility of reverse associations. Finally, enrichment analyses were used to investigate the biofunction.

RESULTS

After correction, three microbial taxa were identified to be causally associated with diverse joint OA (P_FDR < 0.100), namely Methanobacteriaceae family for knee OA (P_FDR = 0.043) and any OA (P_FDR = 0.028), Desulfovibrionales order for knee OA (P_FDR = 0.045) and Ruminiclostridium5 genus for knee OA (P_FDR = 0.063). In addition, we also identified five suggestive microbial taxa that were significant with three different methods under the nominal significance (P < 0.05). Sensitive analysis excluded the influence of heterogeneity and horizontal pleiotropy and multivariable MR analysis ruled out the possibility of horizontal pleiotropy of BMI. GO enrichment analysis illustrates the protective mechanism of the identified taxa against OA.

CONCLUSIONS

This study found that several microbial taxa were causally associated with diverse joint OA. The results enhanced our understanding of gut microbiota in the pathology of OA.

Gut permeability and osteoarthritis, towards a mechanistic understanding of the pathogenesis: a systematic review

Osteoarthritis (OA) is the most common condition affecting human joints. Along with mechanical and genetic factors, low-grade inflammation is increasingly supported as a causal factor in the development of OA. Gut microbiota and intestinal permeability, via the disruption of tight junction competency, are proposed to explain a gut-joint axis through the interaction with the host immune system. Since previous studies and methods have underestimated the role of the gut-joint axis in OA and have only focussed on the characterisation of microbiota phenotypes, this systematic review aims to appraise the current evidence concerning the influence of gut permeability in the pathogenesis of OA. We propose that the tight junction disruption may be due to an increase in zonulin activity as already demonstrated for many other chronic inflammatory disorders. After years of unreliable quantification, one study optimised the methodology, showing a positive validated correlation between plasma lipopolysaccharide (LPS), obesity, joint inflammation, and OA severity. Chemokines show a prominent role in pain development. Our systematic review confirms preliminary evidence supporting a gut-joint axis in OA pathogenesis and progression. Being modifiable by several factors, the gut microbiota is a promising target for treatment. We propose a pathogenetic model in which dysbiosis is correlated to the bipartite graph of tight junctions and bacterially-produced products, aiming to direct future studies in the search of other bacterial products and tight junction disassembly regulators.KEY MESSAGESPrevious studies and methods have underestimated the impact of the gut-joint axis in osteoarthritis and have focussed on the characterisation of microbiota phenotypes rather than clear molecular mediators of disease.Gut dysbiosis is related to higher levels of bacterial toxins that elicit cartilage and synovium inflammatory pathways.Future research may benefit from focussing on both tight junctions and bacterially-produced products.

Alteration of the gut microbiota in rhesus monkey with spontaneous osteoarthritis

Background

The spontaneous osteoarthritis (OA) in rhesus macaque is similar to OA in human, which maintains an upright body posture and shows very similar biomechanical properties of bones to humans. At present, there is no good treatment for OA. This study aims to explore relationship between OA and intestinal microbiota, and provide a reference for the treatment of clinical OA.

Results

We collected colonic contents of the 20 rhesus macaque (6–15 years old, female) for intestinal microbiota analysis by metagenomics sequencing, of which 10 were spontaneous OA monkeys and 10 were normal monkeys. Our results showed the diversity of gut microbiota in monkeys with OA was decreased compared to the normal monkeys (p = 0.16). Mollicutes, Tenericutes, Coprobacillus and Faecalitalea may be biomarkers for the monkeys of OA. Lactobacillus found significantly increased in OA monkeys. Prevotella and Ruminococcus were higher in the normal group than OA group. Zinc/manganese transport system permease protein (p = 0.0011) and Cyclopropane-fatty-acyl-phospholipid synthase (p = 0.0012) are a microbiota metabolic pathway related to cartilage production.

Conclusions

Our results indicate that the diversity and composition of intestinal microbiota in monkeys with OA are different compared to the normal monkeys. we have found microbes that may be a biomarker for the diagnosis of osteoarthritis. Functional analysis of the microbiota also predicts cartilage damage in the monkeys with osteoarthritis. Non-human primates are closely related to humans, so this study can provide a reference for the development of drugs for the treatment of OA.

The risk of revision following total hip arthroplasty in patients with inflammatory bowel disease, a registry based study

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the intestinal tract and is associated with decreased bone mineral density. IBD patients are at higher risk of osteopenia, osteoporosis and fracture compared to non-IBD patients. The impact of IBD on the performance of orthopedic implants has not been well studied. We hypothesized that a history of IBD at the time of primary total hip arthroplasty (THA) would increase the risk of subsequent failure as assessed by revision surgery. A retrospective implant survival analysis was completed using the Swedish Hip Arthroplasty Registry and the Sweden National Patient Register. A total of 150,073 patients undergoing THA for osteoarthritis within an 18-year period were included in the study. THA patients with (n = 2,604) and without (n = 147,469) a history of IBD at the time of THA were compared with primary revision as the main endpoint and adjusted using sex, age category and comorbidity (Elixhauser scores) as covariates. We found that patients with a history of IBD had a relatively higher risk of revision surgery for septic causes while the non-IBD patients had a relatively higher risk of revision for aseptic causes (p = 0.004). Our findings suggest there may be an association between gut health and THA performance.

A White Paper on Collagen Hydrolyzates and Ultrahydrolyzates: Potential Supplements to Support Joint Health in Osteoarthritis?

PURPOSE OF REVIEW

Osteoarthritis (OA) is the most common forms of arthritis in the general population, accounting for more pain and functional disability than any other musculoskeletal disease. There are currently no approved disease modifying drugs for OA. In the absence of effective pharmacotherapy, many patients with OA turn to nutritional supplements and nutraceuticals, including collagen derivatives. Collagen hydrolyzates and ultrahydrolyzates are terms used to describe collagens that have been broken down into small peptides and amino acids in the presence of collagenases and high pressure.

RECENT FINDINGS

This article reviews the relevant literature and serves as a White Paper on collagen hydrolyzates and ultrahydrolyzates as emerging supplements often advertised to support joint health in OA. Collagen hydrolyzates have demonstrated some evidence of efficacy in a handful of small scale clinical trials, but their ability to treat and reverse advanced joint disease remains highly speculative, as is the case for other nutritional supplements. The aim of this White Paper is to stimulate research and development of collagen-based supplements for patients with OA and other musculoskeletal diseases at academic and industrial levels. This White Paper does not make any treatment recommendations for OA patients in the clinical context, but simply aims to highlight opportunities for scientific innovation and interdisciplinary collaboration, which are crucial for the development of novel products and nutritional interventions based on the best available and published evidence.

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

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

Potential roles of 1,5-anhydro-D-fructose in modulating gut microbiome in mice

The gut microbiota has tremendous potential to affect the host’s health, in part by synthesizing vitamins and generating nutrients from food that is otherwise indigestible by the host. 1,5-Anhydro-d-fructose (1,5-AF) is a monosaccharide with a wide range of bioactive potentials, including anti-oxidant, anti-inflammatory, and anti-microbial effects. Based on its potential benefits and minimal toxicity, it is anticipated that 1,5-AF will be used as a dietary supplement to support general health. However, the effects of 1,5-AF on the gut microbiota are yet to be clarified. Here, using an unbiased metagenomic approach, we profiled the bacterial taxa and functional genes in the caecal microbiota of mice fed a diet containing either 2% 1,5-AF or a reference sweetener. Supplementation with 1,5-AF altered the composition of the gut microbiota, enriching the proportion of Faecalibacterium prausnitzii. 1,5-AF also altered the metabolomic profile of the gut microbiota, enriching genes associated with nicotinamide adenine dinucleotide biosynthesis. These findings support the potential benefits of 1,5-AF, but further studies are required to clarify the impact of 1,5-AF on health and disease.

Responses to an intra-articular lipopolysaccharide challenge following dietary supplementation of Saccharomyces cerevisiae fermentation product in young horses

Dietary intervention may be a valuable strategy to optimize the intra-articular environment in young horses to prolong their performance career. To test the hypothesis that dietary supplementation of a Saccharomyces cerevisiae fermentation product would reduce markers of joint inflammation and increase markers of cartilage metabolism following a single inflammatory insult, Quarter Horse yearlings (mean ± SD; 9 ± 1.0 mo) were balanced by age, sex, body weight (BW), and farm of origin and randomly assigned to the following treatment groups: 1.25% BW/d (dry matter basis) custom-formulated concentrate only (CON; n = 9) or concentrate top-dressed with 21 g/d S. cerevisiae fermentation product (SCFP; n = 10) for 98 d. Horses had ad libitum access to Coastal bermudagrass hay. On day 84, one randomly selected radial carpal joint from each horse was injected with 0.5 ng lipopolysaccharide (LPS) solution. The remaining carpal joint was injected with sterile lactated Ringer’s solution as a contralateral control. Synovial fluid obtained before supplementation (day 0) and on day 84 at preinjection hour 0 and 6, 12, 24, 168, and 336 h postinjection was analyzed for prostaglandin E₂ (PGE₂), carboxypropeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C) by commercial assays. Rectal temperature, heart rate, respiration rate, carpal surface temperature, and carpal circumference were recorded prior to each sample collection and for 24 h postinjection. Data were analyzed using linear models with repeated measures. From day 0 to 84, synovial C2C declined (P ≤ 0.01) and the CPII:C2C ratio increased (P ≤ 0.01) in all horses with no effect of diet. In response to intra-articular LPS, synovial PGE₂ increased by hour 6 (P ≤ 0.01) and returned to baseline by hour 336; CPII increased by hour 12, remained elevated through hour 168 (P ≤ 0.01), and returned to baseline by hour 336; and C2C increased by hour 6 (P ≤ 0.01) but did not return to baseline through hour 336 (P ≤ 0.01). Post-intra-articular injection, PGE₂ levels were lower in SCFP than CON horses (P = 0.01) regardless of injection type. Synovial CPII and the CPII:C2C ratio demonstrated stability during the LPS challenge in SCFP compared with CON horses (P ≤ 0.01). Clinical parameters were not influenced by diet but increased in response to repeated arthrocentesis (P ≤ 0.01). Dietary SCFP may favorably modulate intra-articular inflammation following an acute stressor and influence cartilage turnover in young horses.

Nrf2 Regulates CHI3L1 to Suppress Inflammation and Improve Post-Traumatic Osteoarthritis

Introduction

Post-traumatic osteoarthritis (PTOA) is an inflammatory condition that occurs following mechanical joint trauma and that results in joint degeneration. This study sought to evaluate the regulatory function of nuclear factor erythroid 2-related factor 2 (Nrf2) in a murine model of anterior cruciate ligament transection (ACLT)-induced PTOA and in an in vitro model of synoviocyte inflammation induced by LPS treatment with the goal of exploring the role of chitinase 3-like-1 (CHI3L1) in this pathogenic context.

Methods

PTOA model mice were intra-articularly injected with Nrf2 overexpression lentiviral vector, and safranin O-fast green staining as well as the Osteoarthritis Research Society International (OARSI) Scoring System were used to evaluate the severity of cartilage damage. Protein expression in the synovial tissue was evaluated by Western blotting, immunohistochemical staining, and ELISA. Additionally, murine synoviocytes were infected with Nrf2 overexpression lentivirus and stimulated with LPS. The levels of inflammatory cytokines were detected by ELISA. ROS levels were measured using dihydroethidium (DHE) dye.

Results

We determined that the overexpression of Nrf2 was sufficient to reduce cartilage degradation in the context of PTOA in vivo, and we observed a significant decrease in the expression of matrix metalloproteinase 13 (MMP13) in the articular cartilage of samples from mice overexpressing Nrf2 relative to control mice. Synovial CHI3L1 expression and serum TNF-α, IL-1β, and IL-6 levels were reduced in animals overexpressing this transcription factor relative to PTOA model controls. Consistent with these findings, murine synoviocytes treated with LPS exhibited dose-dependent increases in ROS, TNF-α, IL-1β, IL-6, Nrf2, and CHI3L1 levels, whereas Nrf2 overexpression was sufficient to suppress these increases.

Conclusion

Our data indicated that Nrf2 negatively regulates CHI3L1, suggesting that this signaling axis may regulate PTOA progression and may thus be a viable therapeutic target in individuals affected by this condition.

Musculoskeletal Microbiology: The Microbiome in Orthopaedic Biomechanics

Orthopaedic biomechanics and bioengineering is a founding discipline of biomedical engineering that focuses on the effects of mechanical stress and strain on musculoskeletal tissues during growth, function and repair. In the past decade the gut microbiome has emerged as a contributor to disease processes throughout the body, but only recently has been shown to influence orthopaedic biomechanics. Here I review emergent findings showing that the gut microbiome can regulate important aspects of the musculoskeletal system including growth and development; tissue failure and disease; and orthopaedic surgery. These early findings suggest that the microbiome may help answer questions in orthopaedic biomechanics that are not well addressed by current interventions, and highlights the promise of the emerging field of "Musculoskeletal Microbiology".

Gastrointestinal Digestion Model Assessment of Peptide Diversity and Microbial Fermentation Products of Collagen Hydrolysates

Osteoarthritis (OA), the most common form of arthritis, is associated with metabolic diseases and gut microbiome dysbiosis. OA patients often take supplements of collagen hydrolysates (CHs) with a high peptide content. Following digestion, some peptides escape absorption to induce prebiotic effects via their colonic fermentation to generate short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs) and colonic gases (NH₄ and H₂S). The capacity of CHs to generate microbial metabolites is unknown. Proteomic analysis of two CHs (CH-GL and CH-OPT) demonstrated different native peptide profiles with increased peptide diversity after in vitro gastric and small intestinal digestion. Subsequent 24 h fermentation of the CH digests in a dynamic gastrointestinal (GI) digestion model containing human fecal matter showed that CH-OPT increased (p < 0.05) H₂S, SCFAs (propionic, butyric and valeric acids), BCFAs, and decreased NH₄ in the ascending colon reactor with no major changes seen with CH-GL. No major effects were observed in the transverse and descending vessels for either CH. These findings signify that CHs can induce prebiotic effects in the ascending colon that are CH dependent. More studies are needed to determine the physiological significance of CH-derived colonic metabolites, in view of emerging evidence connecting the gut to OA and metabolic diseases.

Polysaccharide from Flammulina velutipes attenuates markers of metabolic syndrome by modulating the gut microbiota and lipid metabolism in high fat diet-fed mice

Natural biological macromolecules with putative functions of gut microbiota regulation possess the advantage of improving metabolic syndrome (MS). In this research, we aimed to determine the effects of Flammulina velutipes polysaccharide (FVP) (Expt. 1) and fecal microbiota transplantation (FMT) (Expt. 2) on MS-related disorders, gut microbiota structure changes and their underlying mechanisms in a murine model fed with high-fat diet (HFD). In Expt. 1, six-week-old male C57BL/6J mice were fed with a control diet (10% calories from fat) or a high fat diet (45% calories from fat), administered with saline or FVP (0.4 mg per g b.w.) by gavage over a 12-week period. In Expt. 2, mice were fed with a HFD, administered with fecal supernatants from healthy and FVP-fed donor mice for 12 weeks simultaneously. The body mass, blood lipid levels and blood glucose homeostasis of mice were analyzed, and total RNA from mouse liver and adipose tissue were extracted by TRIzol and the lipid metabolism-related gene expressions were calculated by qRT-PCR. Gut microbiota changes were evaluated by high-throughput sequencing. Results indicated that FVP and FMT supplementations showed an attenuation effect on mouse obesity, hyperlipidemia and insulin resistance. Up-regulated expressions of Ampkα1 and Ppara were found both in FVP and FMT treatment groups. Different changes were found in the gut microbiota caused by FVP and FMT, respectively. PICRUSt analysis indicated that compared with FVP supplementation, FMT showed a significant effect on regulating lipid metabolism in HFD-fed mice. The findings from this study indicated that oral administrations of FVP or FMT could significantly attenuate MS-related obesity, hyperlipidemia and insulin resistance in HFD-fed mice, and the beneficial effects may be mediated through lipid metabolism and gut microbiota regulation in different ways. These results improve the understanding of the functional activity of FVP as prebiotics.

Low-Dose Lactulose as a Prebiotic for Improved Gut Health and Enhanced Mineral Absorption

Although medium and high doses of lactulose are used routinely for the treatment of constipation and hepatic encephalopathy, respectively, a wealth of evidence demonstrates that, at low doses, lactulose can also be used as a prebiotic to stimulate the growth of health-promoting bacteria in the gastrointestinal tract. Indeed, multiple preclinical and clinical studies have shown that low doses of lactulose enhance the proliferation of health-promoting gut bacteria (e.g., Bifidobacterium and Lactobacillus spp.) and increase the production of beneficial metabolites [e.g., short-chain fatty acids (SCFAs)], while inhibiting the growth of potentially pathogenic bacteria (e.g., certain clostridia). SCFAs produced upon microbial fermentation of lactulose, the most abundant of which is acetate, are likely to contribute to immune regulation, which is important not only within the gut itself, but also systemically and for bone health. Low-dose lactulose has also been shown to enhance the absorption of minerals such as calcium and magnesium from the gut, an effect which may have important implications for bone health. This review provides an overview of the preclinical and clinical evidence published to date showing that low-dose lactulose stimulates the growth of health-promoting gut bacteria, inhibits the growth of pathogenic bacteria, increases the production of beneficial metabolites, improves mineral absorption, and has good overall tolerability. Implications of these data for the use of lactulose as a prebiotic are also discussed.

Specific Pathogen-Free Animals for Civilian and Military Trauma: a Cautionary Note in the Translation of New Drug Therapies

Specific-pathogen free (SPF) animals were introduced into biomedical research in the early 1960s to reduce the incidence of disease into experimental design. The goal was to provide animals with selected microbiota compatible with sustained health. Sixty years later, SPF status has become a variable itself in biomedical research. Alterations in the gut microbiome-host relationship can profoundly influence basic physiology, immune/inflammatory function, susceptibility to infection and disease, and behavior. In addition, it can influence the translational success of a drug or technology from animal models to humans. We discuss this aspect of SPF status in animal models used for military or civilian trauma and shock research. Currently, there is a broad spectrum of SPF exclusion and inclusion criteria which vary from one supplier or animal husbandry facility. If translation to humans is the end-game of trauma research, we recommend replicating a gut microbiome similar to the wild-type for optimal success. We further suggest that at the end of each publication a URL access be provided on Animal Microbial/Pathogen Exclusion Status that a study was based upon. This may help address the differences in results within a single laboratory or between laboratories around the world and improve translation success.

Taxonomic changes in the gut microbiota are associated with cartilage damage independent of adiposity, high fat diet, and joint injury

Lipodystrophic mice are protected from cartilage damage following joint injury. This protection can be reversed by the implantation of a small adipose tissue graft. The purpose of this study was to evaluate the relationship between the gut microbiota and knee cartilage damage while controlling for adiposity, high fat diet, and joint injury using lipodystrophic (LD) mice. LD and littermate control (WT) mice were fed a high fat diet, chow diet, or were rescued with fat implantation, then challenged with destabilization of the medial meniscus surgery to induce osteoarthritis (OA). 16S rRNA sequencing was conducted on feces. MaAslin2 was used to determine associations between taxonomic relative abundance and OA severity. While serum LPS levels between groups were similar, synovial fluid LPS levels were increased in both limbs of HFD WT mice compared to all groups, except for fat transplanted animals. The Bacteroidetes:Firmicutes ratio of the gut microbiota was significantly reduced in HFD and OA-rescued animals when compared to chow. Nine novel significant associations were found between gut microbiota taxa and OA severity. These findings suggest the presence of causal relationships the gut microbiome and cartilage health, independent of diet or adiposity, providing potential therapeutic targets through manipulation of the microbiome.

Baicalin ameliorates Mycoplasma gallisepticum-induced inflammatory injury in the chicken lung through regulating the intestinal microbiota and phenylalanine metabolism

Baicalin shows excellent protective effects against Mycoplasma gallisepticum (MG) induced inflammatory injury as discussed in our previous studies. However, the physiological effects of baicalin are notable in contrast to its low bioavailability, and the critical mechanism for the protective effects of baicalin against MG infection is still unclear. The main objective of this study was to investigate whether baicalin alleviates MG-induced lung inflammatory injury through regulating gut microbiota. Using an MG infection model, results showed that baicalin treatment significantly reduced MG colonization and ameliorated the abnormal pathological changes in the lung. Baicalin treatment also reduced the level of proinflammatory cytokines and suppressed proinflammatory protein expression. Notably, MG infection changed the gut microbiota composition, however, the abnormal gut microbiota composition was partially alleviated by baicalin treatment. Baicalin significantly enriched the commensal bacterium Bacteroides fragilis, and gavaged with Bacteroides fragilis alleviating MG infection-induced inflammatory injury in the lung. In addition, baicalin reversed peripheral accumulation of phenylalanine induced by MG infection. Importantly, increased phenylalanine induced excessive necroptosis through the modulation of gga-miR-190a-3p-Fas-associated protein with death domain (FADD) axis in HD11 macrophages. Together, our findings highlighted the role of gut microbiota and phenylalanine metabolism in MG infection and confirmed that baicalin could effectively inhibit MG-induced inflammatory injury in the lung by remodeling the gut microbiota and phenylalanine metabolism.

Dysbiosis of the gut microbiome is a risk factor for osteoarthritis in older female adults: a case control study

Background

Osteoarthritis (OA) is a multifactorial joint degenerative disease with low-grade inflammation. The gut microbiome has recently emerged as an pathogenic factor of OA, and prebiotics supplementation could alleviate OA symptoms in animal models. However, the relationship between the gut microbiome and OA in the older female adults is hitherto not clear.

Results

Here we studied the gut microbiome of 57 OA patients and their healthy controls by metagenome-wide association study based on previously published data. A significant reduction in the richness and diversity of gut microbiome were observed in OA patients. Bifidobacterium longum and Faecalibacterium prausnitzii were decreased while Clostridium spp. was increased in the OA group. The functional modules, particularly the energetic metabolism and acetate production were also decreased in the OA patients. To evaluate the diagnostic value of identified species for elderly patients with OA, we constructed a set of random forest disease classifiers based on species differences between the two groups. Among them, 9 species reached the lowest classification error in the random forest cross validation, and the area under ROC of the model was 0.81.

Conclusions

Significant alterations in the gut microbial composition and function were observed between the older patients with OA and their controls, and a random forest classifier model for OA were constructed based on the differences in our study. Our study have identified several potential gut microbial targets in the elderly females with OA, which will facilitate the treatment of OA based on gut microbiota, is of great value in alleviating pain and improving the quality of life for them.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04199-0.

The gut microbiome as non-invasive biomarkers for identifying overweight people at risk for osteoarthritis

OBJECTIVE

To evaluate the potential for identifying overweight people at risk for osteoarthritis from a gut microbiome biomarker.

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis, affecting millions of people worldwide. Being overweight increases the load placed on the joints such as the knee, which increases stress and could hasten the breakdown of cartilage. Identifying overweight people at risk for osteoarthritis remains a challenge. However, emerging evidence indicates that microbial dysbiosis in the human gut might play an important role in many inflammatory diseases. Considering the role of inflammation in OA development, analysis of the gut microbiome might be a potential non-invasive tool for overweight individuals to evaluate their risk for OA.

RESULTS

In this prospective study, we collected 182 stool samples from overweight OA patients (n = 86) and overweight normal people (n = 96) (25 kg/m²<BMI<30 kg/m²). 16S ribosomal RNA gene sequencing for V3 and V4 regions on the Illumina MiSeq platform was used to identify bacteria at different levels and it showed that both the diversity and richness of the gut microbiome decreased in overweight OA patients. Correspondingly, 9 phyla and 87 genera had significantly differences between overweight OA patients and overweight normal people. Finally, we identified 7 optimal microbial biomarkers in genus levels as a panel, including Gemmiger, Klebsiella, Akkermansia, Bacteroides, Prevotella, Alistipes and Parabacteroides, to build the random forest model, and achieved a 83.36% area under the curve (AUC) of receiver operating characteristic (ROC).

CONCLUSION

We present the first 16S rRNA gene sequencing profiling study of stool microbiomes in overweight people to discover and validate microbial biomarkers indicating risk for OA. Our study successfully established a 7 biomarkers prediction panel, moving towards affordable non-invasive early diagnostic biomarkers for OA in stool samples from overweight individuals.

Microbiome and osteoarthritis: New insights from animal and human studies

Osteoarthritis (OA) is a common cause of disability, especially among the elderly. With an ageing and increasingly obese population, OA will become more prevalent. Obesity and metabolic syndrome are risk factors for OA and have been implicated in its pathogenesis. The gut microbiome may shed light on this possible common pathogenesis. Recent animal and human studies have gained important insights into the relationship between OA, obesity, and the gut microbiome. Animal studies have demonstrated links between obesity and increased severity of OA and altered gut microbial DNA profile. Use of prebiotics and probiotics in animal trials provides proof-of-concept that interventional options to the gut microbiome can modulate the progression of OA favorably. Current evidence in human studies is limited. Shifts in gut microbial profile and reduced gut microbial diversity have been associated with people with OA, as well as blood and synovial fluid lipopolysaccharide endotoxemia. Linkages between microbiome dysbiosis and host responses may help in the understanding of OA pathogenesis and the discovery of therapeutic targets. This narrative review provides a summary of up-to-date animal and human studies on the gut microbiome and its link with OA.

Obesity and load-induced posttraumatic osteoarthritis in the absence of fracture or surgical trauma

Osteoarthritis is increasingly viewed as a heterogeneous disease with multiple phenotypic subgroups. Obesity enhances joint degeneration in mouse models of posttraumatic osteoarthritis (PTOA). Most models of PTOA involve damage to surrounding tissues caused by surgery/fracture; it is unclear if obesity enhances cartilage degeneration in the absence of surgery/fracture. We used a nonsurgical animal model of load-induced PTOA to determine the effect of obesity on cartilage degeneration 2 weeks after loading. Cartilage degeneration was caused by a single bout of cyclic tibial loading at either a high or moderate load magnitude in adult male mice with severe obesity (C57Bl6/J + high-fat diet), mild obesity (toll-like receptor 5 deficient mouse [TLR5KO]), or normal adiposity (C57Bl6/J mice + normal diet and TLR5KO mice in which obesity was prevented by manipulation of the gut microbiome). Two weeks after loading, cartilage degeneration occurred in limbs loaded at a high magnitude, as determined by OARSI scores (P < .001). However, the severity of cartilage damage did not differ among groups. Osteophyte width and synovitis of loaded limbs did not differ among groups. Furthermore, obesity did not enhance cartilage damage in limbs evaluated 6 weeks after loading. Constituents of the gut microbiota differed among groups. Our findings suggest that, in the absence of surgery/fracture, obesity may not influence cartilage loss after a single mechanical insult, suggesting that either damage to surrounding tissues or repeated mechanical insult is necessary for obesity to influence cartilage degeneration. These findings further illustrate heterogeneity in PTOA phenotypes and complex interactions between mechanical/metabolic factors in cartilage loss.

Oral Administration of Lactobacillus rhamnosus Ameliorates the Progression of Osteoarthritis by Inhibiting Joint Pain and Inflammation

Osteoarthritis (OA) is the most common form of arthritis and age-related degenerative joint disorder, which adversely affects quality of life and causes disability. However, the pathogenesis of OA remains unclear. This study was performed to examine the effects of Lactobacillus rhamnosus in OA progression. OA was induced in 6-week-old male Wistar rats by monosodium iodoacetate (MIA) injection, and the effects of oral administration of L. rhamnosus were examined in this OA rat model. Pain severity, cartilage destruction, and inflammation were measured in MIA-induced OA rats. The small intestines were isolated from OA rats, and the intestinal structure and inflammation were measured. Protein expression in the dorsal root ganglion was analyzed by immunohistochemistry. The effects of L. rhamnosus on mRNA and protein expression in chondrocytes stimulated with interleukin (IL)-1β and lipopolysaccharide (LPS) were analyzed by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Pain severity was decreased in L. rhamnosus-treated MIA-induced OA rats. The levels of expression of MCP-1, a potential inflammatory cytokine, and its receptor, CCR2, were decreased, and GABA and PPAR-γ expression were increased in L. rhamnosus-treated OA rats. The inflammation, as determined by IL-1β, and cartilage destruction, as determined by MMP3, were also significantly decreased by L. rhamnosus in OA rats. Additionally, intestinal damage and inflammation were improved by L. rhamnosus. In human OA chondrocytes, TIMP1, TIMP3, SOX9, and COL2A1 which are tissue inhibitors of MMP, and IL-10, an anti-inflammatory cytokine, were increased by L. rhamnosus. L. rhamnosus treatment led to decreased pain severity and cartilage destruction in a rat model of OA. Intestinal damage and inflammation were also decreased by L. rhamnosus treatment. Our findings suggested the therapeutic potential of L. rhamnosus in OA.

Effect of a prebiotic supplement on knee joint function, gut microbiota, and inflammation in adults with co-morbid obesity and knee osteoarthritis: study protocol for a randomized controlled trial

BACKGROUND

Osteoarthritis (OA) is a chronic and painful condition where the articular cartilage surfaces progressively degenerate, resulting in loss of function and progressive disability. Obesity is a primary risk factor for the development and progression of knee OA, defined as the "metabolic OA" phenotype. Metabolic OA is associated with increased fat deposits that release inflammatory cytokines/adipokines, thereby resulting in systemic inflammation which can contribute to cartilage degeneration. There is currently no cure for OA. Prebiotics are a type of dietary fiber that can positively influence gut microbiota thereby reducing systemic inflammation and offering protection of joint integrity in rodents. However, no human clinical trials have tested the effects of prebiotics in adults with obesity suffering from knee OA. Therefore, the purpose of this double-blind, placebo-controlled, randomized trial is to determine if prebiotic supplementation can, through positive changes in the gut microbiota, improve knee function and physical performance in adults with obesity and knee OA.

METHODS

Adults (n = 60) with co-morbid obesity (BMI > 30 kg/m2) and knee OA (Kellgren-Lawrence grade II-III) will be recruited from the Alberta Hip and Knee Clinic and the Rocky Mountain Health Clinic and surrounding community of Calgary, Canada, and randomized (stratified by sex, BMI, and age) to prebiotic (oligofructose-enriched inulin; 16 g/day) or a calorie-matched placebo (maltodextrin) for 6 months. Anthropometrics, performance-based tests, knee pain, serum inflammatory markers and metabolomics, quality of life, and gut microbiota will be assessed at baseline, 3 months, 6 months (end of prebiotic supplementation), and 3 months following the end of the prebiotic supplementation.

CLINICAL SIGNIFICANCE

There is growing pressure on health care systems for aggressive OA treatment such as total joint replacement. Less aggressive, yet effective, conservative treatment options have the potential to address the growing prevalence of co-morbid obesity and knee OA by delaying the need for joint replacement or ideally preventing its need altogether. The results of this clinical trial will provide the first evidence regarding the efficacy of prebiotic supplementation on knee joint function and pain in adults with obesity and knee OA. If successful, the results may provide a simple, safe, and easy to adhere to intervention to reduce knee joint pain and improve the quality of life of adults with co-morbid knee OA and obesity.

TRIAL REGISTRATION

Clinical Trials.gov NCT04172688 . Registered on 21 November 2019.

The Gut Microbiome and Osteoarthritis: A Two-Sample Mendelian Randomization Study

Objective

The aim of this study was to examine if the intestinal microbiome is causally correlated with osteoarthritis (OA) incidence.

Methods

A two-sample Mendelian randomization (MR) study was conducted using inverse variance weighting (IVW), weighted median, and MR-Egger regression techniques Publicly accessible summary statistics dataset of intestinal microbiomes of European descent from genome-wide association studies (GWASs) (a total with 3,326 individuals) was used as an exposure As an outcome, summary data from the GWAS include 3,498 patients with OA of the knee and hip from the arcOGEN sample and 11,009 controls of European descent.

Results

We identified 29 single-nucleotide polymorphisms from GWAS of intestinal microbiomes as instrumental variables The IVW approach found no evidence to suggest a causal relationship between the intestinal microbiota and OA (beta=-0001, standard error [SE]=0004, p=0748) The regression test of MR-Egger showed that the directional pleiotropy was unlikely to be a bias (intercept=0002, SE=0007, p=0697) and the MR-Egger study showed no causal relation between the intestinal microbiota and the OA (beta=-0002, SE=0005, p=0630) The weighted median analysis also did not have indications of a causal relationship between the intestinal microbiota and OA (beta=-0002, SE=0005, p=0630) The MR results calculated using IVW, the median weighted and the MR-Egger regression approaches were consistent.

Conclusion

The findings of the MR analysis did not support a causal relationship between intestinal microbiome and OA risk.

Magnesium in joint health and osteoarthritis

Osteoarthritis (OA) is a prevalent debilitating age-related skeletal disease. The hallmark of OA is the degradation of articular cartilage that cushions the joint during movement. It is characterized by chronic pain and disability. Magnesium, a critical trace element in the human body, plays a pivotal role in metabolism homeostasis and the energy balance. Humans obtain magnesium mainly from the diet. However, inadequate magnesium intake is not uncommon. Moreover, the magnesium status deteriorates with ageing. There has been a growing body of clinical studies pointing to an intimate relationship between dietary magnesium and OA although the conclusion remains controversial. As reported, the magnesium ion concentration is essential to determine cell fate. Firstly, the low-concentration magnesium ions induced human fibroblasts senescence. Magnesium supplementation was also able to mitigate chondrocyte apoptosis, and to facilitate chondrocyte proliferation and differentiation. In this literature review, we will outline the existing evidence in animals and humans. We will also discuss the controversies on plasma or intracellular level of magnesium as the indicator of magnesium status. In addition, we put forward the interplay between dietary magnesium intake and intestinal microbiome to modulate the inflammatory milieu in the conjecture of OA pathogenesis. This leads to an emerging hypothesis that the synergistic effect of magnesium and probiotics may open a new avenue for the prevention and treatment of OA.

Gut-microbiota modulation: The impact of thegut-microbiotaon osteoarthritis

Osteoarthritis (OA) is one of the most common medical conditions affecting > 300 million people globally which represents the formidable public health challenge. Despite its clinical and financial ramifications, there are currently no approved disease modifying OA drugs available and symptom palliation is the only alternative. Currently, the amount of data on the human intestinal microbiome is growing at a high rate, both in health and in various pathological conditions. With an increase in the amount of the accumulated data, there is an expanded understanding that the microbiome provides compelling evidence of a link between thegut microbiomeand development ofOA. The microbiota management tools of probiotics and/or prebiotics or symbiotic have been developed and indeed, commercialized over the past few decades with the expressed purpose of altering the microbiota within the gastrointestinal tract which could be a potentially novel intervention to tackle or prevent OA. However, the mechanisms how intestinal microbiota affects the OA pathogenesis are still not clear and further research targeting specific gut microbiota or its metabolites is still needed to advance OA treatment strategies from symptomatic management to individualized interventions of OA pathogenesis. This article provides an overview of the various preclinical and clinical studies using probiotics and prebiotics as plausible therapeutic options that can restore the gastrointestinal microbiota and its impact on the OA pathogenesis. May be in the near future the targeted alterations of gut microbiota may pave the way for developing new interventions to prevent and treat OA.

The Butyrate-Producing Bacterium Clostridium butyricum Suppresses Clostridioides difficile Infection via Neutrophil- and Antimicrobial Cytokine-Dependent but GPR43/109a-Independent Mechanisms

Short-chain fatty acids, such as butyrate, are major gut microbial metabolites that are beneficial for gastrointestinal health. Clostridium butyricum MIYAIRI588 (CBM588) is a bacterium that produces a robust amount of butyrate and therefore has been used as a live biotherapeutic probiotic in clinical settings. Clostridioides difficile causes life-threatening diarrhea and colitis. The gut resident microbiota plays a critical role in the prevention of C. difficile infection (CDI), as the disruption of the healthy microbiota by antibiotics greatly increases the risk for CDI. We report that CBM588 treatment in mice significantly improved clinical symptoms associated with CDI and increased the number of neutrophils and Th1 and Th17 cells in the colonic lamina propria in the early phase of CDI. The protective effect of CBM588 was abolished when neutrophils, IFN-γ, or IL-17A were depleted, suggesting that induction of the immune reactants is required to elicit the protective effect of the probiotic. The administration of tributyrin, which elevates the concentration of butyrate in the colon, also increased the number of neutrophils in the colonic lamina propria, indicating that butyrate is a potent booster of neutrophil activity during infection. However, GPR43 and GPR109a, two G protein-coupled receptors activated by butyrate, were dispensable for the protective effect of CBM588. These results indicate that CBM588 and butyrate suppress CDI, in part by boosting antimicrobial innate and cytokine-mediated immunity.

Musculoskeletal microbiology: The utility of the microbiome in orthopedics

The past 15 years have witnessed a renaissance in the study of the microbes that colonize the human body. The vast majority of the human microbiome resides within the gut. Alterations to the gut microbiome have been associated with the pathogenesis and progression of wide-ranging diseases throughout the body-including atherosclerosis, depression, and obesity. Our understanding of the effects of the gut microbiome on the musculoskeletal system remains in its infancy, but preclinical work has demonstrated an effect of the gut microbiome on the success of orthopedic surgical procedures, osteoporosis, osteoarthritis, and muscle mass. In this perspective I review preclinical findings demonstrating that an impaired presurgical gut microbiome can increase the likelihood of developing periprosthetic joint infection and how alterations in the gut microbiome can reduce bone strength by impairing bone tissue material properties. In addition to discussing these examples, I review the hypothesis that many chronic non-communicable diseases have become more prevalent in modern industrialized societies as a result of changes in the composition of the gut microbiome resulting from changes in environment/lifestyle (diet, sanitation, antibiotic use). The most burdensome musculoskeletal disorders are chronic and non-communicable and may therefore be related to generational shifts in the composition of the gut microbiome, a possibility I illustrate by reviewing changes in the prevalence of osteoarthritis over the last century. Microbiome-based therapeutics are potentially innocuous, inexpensive, and have the potential to be effective with only occasional use, making them attractive for addressing the needs of chronic and/or slowly progressing musculoskeletal disorders.

The gut microbiota in osteoarthritis: where do we stand and what can we do?

Osteoarthritis (OA) is one of the most frequent musculoskeletal diseases characterized by degeneration of articular cartilage, subchondral bone remodeling, and synovial membrane inflammation, which is a leading cause of global disability, morbidity, and decreased quality of life. Interpreting the potential mechanisms of OA pathogenesis is essential for developing novel prevention and disease-modifying therapeutic interventions. Gut microbiota is responsible for a series of metabolic, immunological, and structural and neurological functions, potentially elucidating the heterogeneity of OA phenotypes and individual features. In this narrative review, we summarized research evidence supporting the hypothesis of a “gut-joint axis” and the interaction between gut microbiota and the OA-relevant factors, including age, gender, genetics, metabolism, central nervous system, and joint injury, elucidating the underlying mechanisms of this intricate interaction. In the context, we also speculated the promising manipulation of gut microbiota in OA management, such as exercise and fecal microbiota transplantation (FMT), highlighting the clinical values of gut microbiota. Additionally, future research directions, such as more convincing studies by the interventions of gut microbiota, the gene regulation of host contributing to or attributed to the specific phenotypes of gut microbiota related to OA, and the relevance of distinct cell subgroups to gut microbiota, are expected. Moreover, gut microbiota is also the potential biomarker related to inflammation and gut dysbiosis that is able to predict OA progression and monitor the efficacy of therapeutic intervention.

The gut microbiome-joint connection: implications in osteoarthritis

Supplemental Digital Content is available in the text

Osteoarthritis is a debilitating disease leading to joint degeneration, inflammation, pain, and disability. Despite efforts to develop a disease modifying treatment, the only accepted and available clinical approaches involve palliation. Although many factors contribute to the development of osteoarthritis, the gut microbiome has recently emerged as an important pathogenic factor in osteoarthritis initiation and progression. This review examines the literature to date regarding the link between the gut microbiome and osteoarthritis.

Gut microbiota influence tumor development and Alter interactions with the human immune system

Recent scientific advances have greatly enhanced our understanding of the complex link between the gut microbiome and cancer. Gut dysbiosis is an imbalance between commensal and pathogenic bacteria and the production of microbial antigens and metabolites. The immune system and the gut microbiome interact to maintain homeostasis of the gut, and alterations in the microbiome composition lead to immune dysregulation, promoting chronic inflammation and development of tumors. Gut microorganisms and their toxic metabolites may migrate to other parts of the body via the circulatory system, causing an imbalance in the physiological status of the host and secretion of various neuroactive molecules through the gut-brain axis, gut-hepatic axis, and gut-lung axis to affect inflammation and tumorigenesis in specific organs. Thus, gut microbiota can be used as a tumor marker and may provide new insights into the pathogenesis of malignant tumors.

Lactobacillus salivarius ameliorated Mycoplasma gallisepticum-induced inflammatory injury and secondary Escherichia coli infection in chickens: Involvement of intestinal microbiota

Mycoplasma gallisepticum (MG) infection alone or in combination with other pathogens have brought huge economic losses to the poultry industry. The intestinal microbiota plays a critical role in host defence against respiratory infection. To explore the role of intestinal microbiota in MG-induced inflammation-mediated lung injury and secondary Escherichia coli infection, MG infection model and fecal microbiota transplantation model were developed. The results showed that MG infection changed gut microbiota composition along with lung inflammation injury. Fecal microbiota transplantation from chickens infected with MG to antibiotics cocktail treated chickens decreased host defense against Escherichia coli due to impaired intestinal mucosal barrier, downregulated the mRNA expression levels of host defense enzymes and blocked autophagic flux. Lactobacillus salivarius intake alleviated lung inflammation injury caused by MG infection and increased host defense against Escherichia coli by improved gut microbiota composition. These results highlighted the role of gut microbiota in MG-infection induced lung inflammation injury and secondary infection that offered a new strategy for preventive intervention against MG infection.

Combination of Treadmill Aerobic Exercise with Bifidobacterium longum OLP-01 Supplementation for Treatment of High-Fat Diet-Induced Obese Murine Model

INTRODUCTION

Obesity, which can result from disease, genetics, nutrition, lifestyle, and insufficient physical activity, substantially increases an individual's risk of complications and comorbidities. Exercise can be an effective strategy for achieving an energy balance and physiological fitness as part of obesity management. Additionally, probiotics, which are isolated from food and the environment, are being rapidly developed and have functional benefits for mitigating various metabolic dysfunctions associated with obesity. The potentially positive physiological and functional effects of exercise, probiotics, and exercise combined with probiotics should be elucidated in a model of diet-induced obesity.

METHODS

Bifidobacterium longum subsp. longum OLP-01 (OLP-01) was isolated from an elite Olympic-level athlete who exhibited physiological adaptations to peripheral fatigue caused by exercise training. In this current study, ICR strain mice were fed a high-fat diet (HFD) for 4 weeks to replicate an obesity model. The mice were divided into 5 groups according to the diet administered: control with normal diet, only HFD, HFD + exercise, HFD + OLP, and HFD + exercise + OLP groups. They were administered the probiotic and/or treadmill exercise training for 5 weeks, and their growth curve, physical activity, physiological adaptation, biochemical parameters, body composition, and glucose tolerance were assessed.

RESULTS

Compared with only exercise or only probiotics, a combination of probiotics and exercise significantly improved the weight, glucose tolerance, fat composition, and exercise-related oxidative stress of mice. Regular and programmed exercise with sufficient rest may be crucial to obesity improvement, and a combination of probiotics and exercise may synergistically assist obesity management and health promotion.

CONCLUSION

OLP-01 probiotics combined with exercise training can be employed as a strategy for treating obesity. However, the exact regulatory mechanisms underlying this effect, possibly involving microbiota and associated metabolites, warrant further investigation.

Gut microbiome dysbiosis alleviates the progression of osteoarthritis in mice

Gut microbiota dysbiosis has been studied under the pathological conditions of osteoarthritis (OA). However, the effect of antibiotic-induced gut flora dysbiosis on OA remains incompletely understood at present. Herein, we used a mouse (8 weeks) OA model of destabilization of the medial meniscus (DMM) and gut microbiome dysbiosis induced by antibiotic treatment with ampicillin and neomycin for 8 weeks. The results show that antibiotic-induced intestinal microbiota dysbiosis reduced the serum level of lipopolysaccharide (LPS) and the inflammatory response, such as suppression of the levels of tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6), which can lead to decreased matrix metalloprotease-13 (MMP-13) expression and improvement of OA after joint injury. In addition, trabecular thickness (Tb.Th) and osteophyte scores were increased significantly in antibiotic-induced male mice compared with female mice. We further used network correlation analysis to verify the effect of gut microbiota dysbiosis on OA. Therefore, the present study contributes to our understanding of the gut-joint axis in OA and reveals the relationship between the inflammatory response, sex and gut microbiota, which may provide new strategies to prevent the symptoms and long-term sequelae of OA. Conclusion: Our data showed that gut microbiome dysbiosis alleviates the progression of OA.

Identification and Characterization of the Intra-Articular Microbiome in the Osteoarthritic Knee

Osteoarthritis (OA) is the most common joint disorder in the United States, and the gut microbiome has recently emerged as a potential etiologic factor in OA development. Recent studies have shown that a microbiome is present at joint synovia. Therefore, we aimed to characterize the intra-articular microbiome within osteoarthritic synovia and to illustrate its role in OA disease progression. RNA-sequencing data from OA patient synovial tissue was aligned to a library of microbial reference genomes to identify microbial reads indicative of microbial abundance. Microbial abundance data of OA and normal samples was compared to identify differentially abundant microbes. We computationally explored the correlation of differentially abundant microbes to immunological gene signatures, immune signaling pathways, and immune cell infiltration. We found that microbes correlated to OA are related to dysregulation of two main functional pathways: increased inflammation-induced extracellular matrix remodeling and decreased cell signaling pathways crucial for joint and immune function. We also confirmed that the differentially abundant and biologically relevant microbes we had identified were not contaminants. Collectively, our findings contribute to the understanding of the human microbiome, well-known OA risk factors, and the role microbes play in OA pathogenesis. In conclusion, we present previously undiscovered microbes implicated in the OA disease progression that may be useful for future treatment purposes.

Dysregulated Autophagy Mediates Sarcopenic Obesity and Its Complications via AMPK and PGC1α Signaling Pathways: Potential Involvement of Gut Dysbiosis as a Pathological Link

Sarcopenic obesity (SOB), which is closely related to being elderly as a feature of aging, is recently gaining attention because it is associated with many other age-related diseases that present as altered intercellular communication, dysregulated nutrient sensing, and mitochondrial dysfunction. Along with insulin resistance and inflammation as the core pathogenesis of SOB, autophagy has recently gained attention as a significant mechanism of muscle aging in SOB. Known as important cellular metabolic regulators, the AMP-activated protein kinase (AMPK) and the peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α) signaling pathways play an important role in autophagy, inflammation, and insulin resistance, as well as mutual communication between skeletal muscle, adipose tissue, and the liver. Furthermore, AMPK and PGC-1α signaling pathways are implicated in the gut microbiome-muscle axis. In this review, we describe the pathological link between SOB and its associated complications such as metabolic, cardiovascular, and liver disease, falls and fractures, osteoarthritis, pulmonary disease, and mental health via dysregulated autophagy controlled by AMPK and/or PGC-1α signaling pathways. Here, we propose potential treatments for SOB by modulating autophagy activity and gut dysbiosis based on plausible pathological links.

The gut microbiota may be a novel pathogenic mechanism in loosening of orthopedic implants in rats

Particles released from implants cause inflammatory bone loss, which is a key factor in aseptic loosening, the most common reason for joint replacement failure. With the anticipated increased incidence of total joint replacement in the next decade, implant failure will continue to burden patients. The gut microbiome is increasingly recognized as an important factor in bone physiology, however, its role in implant loosening is currently unknown. We tested the hypothesis that implant loosening is associated with changes in the gut microbiota in a preclinical model. When the particle challenge caused local joint inflammation, decreased peri-implant bone volume, and decreased implant fixation, the gut microbiota was affected. When the particle challenge did not cause this triad of local effects, the gut microbiota was not affected. Our results suggest that cross-talk between these compartments is a previously unrecognized mechanism of failure following total joint replacement.

Antibiotic Treatment Prior to Injury Improves Post-Traumatic Osteoarthritis Outcomes in Mice

Osteoarthritis (OA) is a painful and debilitating disease characterized by the chronic and progressive degradation of articular cartilage. Post-traumatic OA (PTOA) is a secondary form of OA that develops in ~50% of cases of severe articular injury. Inflammation and re-occurring injury have been implicated as contributing to the progression of PTOA after the initial injury. However, there is very little known about external factors prior to injury that could affect the risk of PTOA development. To examine how the gut microbiome affects PTOA development we used a chronic antibiotic treatment regimen starting at weaning for six weeks prior to ACL rupture, in mice. A six-weeks post-injury histological examination showed more robust cartilage staining on the antibiotic (AB)-treated mice than the untreated controls (VEH), suggesting slower disease progression in AB cohorts. Injured joints also showed an increase in the presence of anti-inflammatory M2 macrophages in the AB group. Molecularly, the phenotype correlated with a significantly lower expression of inflammatory genes Tlr5, Ccl8, Cxcl13, and Foxo6 in the injured joints of AB-treated animals. Our results indicate that a reduced state of inflammation at the time of injury and a lower expression of Wnt signaling modulatory protein, Rspo1, caused by AB treatment can slow down or improve PTOA outcomes.

Moderate exercise ameliorates osteoarthritis by reducing lipopolysaccharides from gut microbiota in mice

Lipopolysaccharides (LPSs) released by gut microbiota are correlated with the pathophysiology of osteoarthritis (OA). Exercise remodels the composition of gut microbiota. The present study investigated the hypothesis that wheel-running exercise prevents knee OA induced by high-fat diet (HFD) via reducing LPS from intestinal microorganisms. Male C57BL/6 J mice were treated with sedentary or wheel-running exercise, standard diet (13.5% kcal) or HFD (60% kcal), berberine or not according to their grouping. Knee OA severity, blood and synovial fluid LPS, cecal microbiota, and TLR4 and MMP-13 expression levels were determined. Our findings reveal that HFD treatment decreased gut microbial diversity. Increase in endotoxin-producing bacteria, decrease in gut barrier-protecting bacteria, high LPS levels in the blood and synovial fluid, high TLR4 and MMP-13 expression levels, and severe cartilage degeneration were observed. By contrast, voluntary wheel running caused high gut microbial diversity. The gut microbiota were reshaped, LPS levels in the blood and synovial fluid and TLR4 and MMP-13 expression levels were low, and cartilage degeneration was ameliorated. Berberine treatment reduced LPS levels in the samples, but decreased the diversity of intestinal flora with similar changes to that caused by HFD. In conclusion, unlike taking drugs, exercising can remodel gut microbial ecosystems, reduce the circulating levels of LPS, and thereby contribute to the relief of chronic inflammation and OA. Our findings showed that moderate exercise is a potential therapeutic approach for preventing and treating obesity-related OA.

Pathogenesis of Osteoarthritis: Risk Factors, Regulatory Pathways in Chondrocytes, and Experimental Models

As the most common chronic degenerative joint disease, osteoarthritis (OA) is the leading cause of pain and physical disability, affecting millions of people worldwide. Mainly characterized by articular cartilage degradation, osteophyte formation, subchondral bone remodeling, and synovial inflammation, OA is a heterogeneous disease that impacts all component tissues of the articular joint organ. Pathological changes, and thus symptoms, vary from person to person, underscoring the critical need of personalized therapies. However, there has only been limited progress towards the prevention and treatment of OA, and there are no approved effective disease-modifying osteoarthritis drugs (DMOADs). Conventional treatments, including non-steroidal anti-inflammatory drugs (NSAIDs) and physical therapy, are still the major remedies to manage the symptoms until the need for total joint replacement. In this review, we provide an update of the known OA risk factors and relevant mechanisms of action. In addition, given that the lack of biologically relevant models to recapitulate human OA pathogenesis represents one of the major roadblocks in developing DMOADs, we discuss current in vivo and in vitro experimental OA models, with special emphasis on recent development and application potential of human cell-derived microphysiological tissue chip platforms.

Probiotic-enriched milk and dairy products increase gut microbiota diversity: a comparative study

Targeting gut microbiota with probiotics has emerged as a promising nutritional approach for the prevention of obesity and metabolic syndrome. Cultured dairy products can be effectively employed for the delivery of probiotics to the gut as well as for the support of growth and survival of probiotic bacteria. The purpose of this study was to characterize the effects of probiotic-enriched pasteurized milk and dairy products (Greek-style yogurt and cottage cheese) of different origins (cow, goat, and camel) on taxonomic composition of the mouse gut microbiota. We hypothesized that cultured dairy products can be an effective vector for the delivery of probiotics to the gut because of its nutritional value, acidic nature, and long shelf-life. Mice were fed a standard low fat, plant polysaccharide-rich (LF/PP) diet supplemented with the probiotic-enriched milk and dairy products for 5 weeks. Next generation sequencing of DNA from mouse fecal samples was used to characterize the bacterial relative abundance. Mice fed a diet supplemented with camel milk demonstrated characteristic changes in the gut microbiota, which included an increase in relative abundance of order Clostridiales and genus Anaerostipes. Mice fed a diet supplemented with the probiotic-enriched cow cheese exhibited an increase in the relative abundance of order Clostridiales, family Ruminococcaceae, and family Lachnospiraceae. The results obtained and their bioinformatics analysis support the conclusion that camel milk and the probiotic cow cheese induce changes in the mouse gut microbiota, which can be characterized as potentially beneficial to health compared to the changes associated with a standard diet. These findings imply that probiotic-enriched milk and dairy products can be highly effective for the delivery and support of probiotic bacteria of the gut.

Electroacupuncture Prevents Osteoarthritis of High-Fat Diet-Induced Obese Rats

The effects of acupuncture on osteoarthritis (OA) pathogenesis have been demonstrated in vitro and in animal models. However, the potential for acupuncture to mediate protective effects on obese-induced OA has not been examined. Here, we investigated the effects of different acupuncture patterns on OA pathogenesis in high-fat diet- (HFD-) induced obese rats. After 12-week diet-induced obesity, obese rats were treated with three acupuncture protocols for 2 weeks, including ST36, GB34, and ST36+GB34. The results showed that the three acupuncture protocols both prevented obesity-induced cartilage matrix degradation and MMP expression and mitigated obesity-induced systemic and local inflammation but had different regulatory effects on lipid metabolism and gut microbiota disorder of obese-induced OA rats. Furthermore, the three acupuncture protocols increased the microbial diversity and altered the structure of community of feces in obese rats. We found that ST36 and GB34 could inhibit proinflammatory shift in the gut microbiome with an increase in the ratio of Bacteroidetes/Firmicutes and promote the recovery of relative abundance of Clostridium, Akkermansia, Butyricimonas, and Lactococcus. Although both ST36 and GB34 had an anti-inflammatory effect on serum inflammatory mediators, only the acupuncture protocol with both ST36 and GB34 could effectively inhibit LPS-mediated joint inflammation in obesity rats. Therefore, relieving obesity-related chronic inflammation, lipid metabolism disorder, and gut microbiota disorder may be an important mechanism for acupuncture with ST36 and GB34 to promote OA recovery.

Identification of Cartilage Microbial DNA Signatures and Associations With Knee and Hip Osteoarthritis

OBJECTIVE

Alterations of the gut microbiota have been implicated in many forms of arthritis, but an examination of cartilage microbial patterns has not been performed. This study was undertaken to characterize the microbial DNA profile of articular cartilage and determine changes associated with osteoarthritis (OA).

METHODS

We performed 16S ribosomal RNA gene deep sequencing on eroded and intact cartilage samples from knee OA patients (n = 21 eroded and 21 intact samples) and hip OA patients (n = 34 eroded and 33 intact samples) and cadaver controls (n = 10 knee samples and 10 hip samples). Microbial DNA diversity was assessed, groups were compared, and metagenomic profiles were reconstructed. Confirmation was performed in an independent cohort by clade-specific quantitative polymerase chain reaction. Findings in human cartilage were compared to those in cartilage from OA-susceptible C57BL/6 (B6) mice and OA-resistant MRL/MpJ (MRL) mice. Germ-free B6 mouse cartilage was analyzed as a methodologic control.

RESULTS

Alpha diversity was reduced in human OA versus control samples (P < 0.0001), and in hip versus knee samples (P < 0.0001). Numerous clades were different in human OA versus control samples, and similar findings were noted in comparisons of murine B6 versus MRL mice. Hip samples were microbiologically distinct from knee samples. OA microbial DNA demonstrated increased gram-negative constituents (P = 0.02). Functional analysis demonstrated increases in lipopolysaccharide production (P = 9.9 × 10-3 ), phosphatidylinositol signaling (P = 4.2 × 10-4 ), and nitrogen metabolism (P = 8 × 10-3 ) and decreases in sphingolipid metabolism (P = 7.7 × 10-4 ) associated with OA.

CONCLUSION

Our study reveals a microbial DNA signature in human and mouse cartilage. Alterations in this signature, including increases in gram-negative constituents, occur during the development and progression of human OA. Furthermore, our findings indicate that strain-specific signatures exist within mouse cartilage that mirror human patterns. Further study of the establishment and potential pathogenic role of these DNA signatures is needed.

Interleukin-1-Interleukin-17 Signaling Axis Induces Cartilage Destruction and Promotes Experimental Osteoarthritis

Osteoarthritis (OA), which is the most common degenerative joint disorder, has been considered a non-inflammatory disease with abnormal mechanics. Interleukin (IL)-17 is a pleiotropic cytokine involved in inflammatory diseases and their production is driven by the cytokine including IL-1 and IL-23. However, little is known about the mechanism of IL-17 in the development of OA. Here, we investigated the role of IL-17 in the pathogenesis of OA using monosodium iodoacetate (MIA)-injected IL-17 and IL-1 receptor antagonist (IL-1Ra) double-deficient mice. In MIA-injected IL-1Ra KO mice, nociceptive properties, degree of cartilage damage, and the level of inflammatory factors in articular cartilage were increased compared to MIA-injected wild-type mice. Interestingly, the intestinal architecture was impaired in IL-1Ra KO mice compared to wild-type mice and the damage was further exacerbated by MIA injection. Deficiency of IL-17 reduced nociceptive properties and cartilage destruction, as well as inflammation-related factors in MIA-injected IL-1Ra KO mice compared to MIA-injected wild-type mice. Furthermore, IL-17-treated chondrocytes from OA patients showed enhanced expression of catabolic factors that are involved in the destruction of cartilage in OA. IL-17 accelerates the destruction of cartilage and small intestine via regulation of several inflammatory mediators in an OA murine model. These results suggest that IL-17 plays a critical role in the development of OA.