Gut microbiota drives metabolic disease in immunologically altered mice

The Role of the Gut Microbiome in Orthopedic Surgery-a Narrative Review

PURPOSE OF REVIEW

The importance of the gut microbiome has received increasing attention in recent years. New literature has revealed significant associations between gut health and various orthopedic disorders, as well as the potential for interventions targeting the gut microbiome to prevent disease and improve musculoskeletal outcomes. We provide a broad overview of available literature discussing the links between the gut microbiome and pathogenesis and management of orthopedic disorders.

RECENT FINDINGS

Human and animal models have characterized the associations between gut microbiome dysregulation and diseases of the joints, spine, nerves, and muscle, as well as the physiology of bone formation and fracture healing. Interventions such as probiotic supplementation and fecal transplant have shown some promise in ameliorating the symptoms or slowing the progression of these disorders. We aim to aid discussions regarding optimization of patient outcomes in the field of orthopedic surgery by providing a narrative review of the available evidence-based literature involving gut microbiome dysregulation and its effects on orthopedic disease. In general, we believe that the gut microbiome is a viable target for interventions that can augment current management models and lead to significantly improved outcomes for patients under the care of orthopedic surgeons.

Metabolite interactions between host and microbiota during health and disease: Which feeds the other?

Metabolites produced by the host and microbiota play a crucial role in how human bodies develop and remain healthy. Most of these metabolites are produced by microbiota and hosts in the digestive tract. Metabolites in the gut have important roles in energy metabolism, cellular communication, and host immunity, among other physiological activities. Although numerous host metabolites, such as free fatty acids, amino acids, and vitamins, are found in the intestine, metabolites generated by gut microbiota are equally vital for intestinal homeostasis. Furthermore, microbiota in the gut is the sole source of some metabolites, including short-chain fatty acids (SCFAs). Metabolites produced by microbiota, such as neurotransmitters and hormones, may modulate and significantly affect host metabolism. The gut microbiota is becoming recognized as a second endocrine system. A variety of chronic inflammatory disorders have been linked to aberrant host-microbiota interplays, but the precise mechanisms underpinning these disturbances and how they might lead to diseases remain to be fully elucidated. Microbiome-modulated metabolites are promising targets for new drug discovery due to their endocrine function in various complex disorders. In humans, metabolotherapy for the prevention or treatment of various disorders will be possible if we better understand the metabolic preferences of bacteria and the host in specific tissues and organs. Better disease treatments may be possible with the help of novel complementary therapies that target host or bacterial metabolism. The metabolites, their physiological consequences, and functional mechanisms of the host-microbiota interplays will be highlighted, summarized, and discussed in this overview.

Female reproductive dysfunctions and the gut microbiota

The gut microbiome is considered an endocrine organ that can influence distant organs and associated biological pathways. Recent advances suggest that gut microbial homeostasis is essential for reproductive health and that perturbations in the gut microbiota can lead to reproductive pathologies. This review provides an updated overview of the relationship between the gut microbiome and female reproductive diseases. Specifically, we highlight the most recent findings on the gut microbiome in gynecological pathologies including polycystic ovarian syndrome, endometriosis, and endometrial cancer. Most studies revealed associations between altered gut microbial compositions and these reproductive diseases, though few have suggested cause-effect relationships. Future studies should focus on determining the molecular mechanisms underlying associations between gut microbiota and reproductive diseases. Understanding this bidirectional relationship could lead to the development of novel and effective strategies to prevent, diagnose, and treat female reproductive organ-related diseases.

High fat diet-induced hyperlipidemia and tissue steatosis in rabbits through modulating ileal microbiota

High-fat diet (HFD) and overnutrition are important starting factors that may alter intestinal microbiota, lipid metabolism, and systemic inflammation. However, there were few studies on how intestinal microbiota contributes to tissue steatosis and hyperlipidemia. Here, we investigated the effect of lipid metabolism disorder-induced inflammation via toll-like receptor 2 (TLR-2), toll-like receptor 4 (TLR-4), and nuclear factor-κB (NF-κB) pathways at the intestinal level in response to HFD. Twenty 80-day-old male New Zealand White rabbits were randomly divided into the normal diet group (NDG) and the high-fat diet group (HDG) for 80 days. Growth performance, blood biochemical parameters, lipid metabolism, inflammation, degree of tissue steatosis, and intestinal microbial composition were measured. HFD increased the relative abundance of Christensenellaceae_R_7_group, Marvinbryantia, Akkermansia etc., with a reduced relative abundance of Enterorhabdus and Lactobacillus. Moreover, HFD caused steatosis in the liver and abdominal fat and abnormal expression of some genes related to lipid metabolism and tight junction proteins. The TLR-2, TLR-4, NF-κB, TNF-α, and IL-6 were confirmed by overexpression with downregulation of IL-10. Serum biochemical indices (TG, TCHO, LDL-C, and HDL-C) were also increased, indicating evidence for the development of the hyperlipidemia model. Correlation analysis showed that this microbial dysbiosis was correlated with lipid metabolism and inflammation, which were associated with the intestinal tract's barrier function and hyperlipidemia. These results provide an insight into the relationship between HFD, the intestinal microbiota, intestinal barrier, tissue inflammation, lipid metabolism, and hyperlipidemia. KEY POINTS: • High-fat diet leads to ileal microbiota disorders • Ileal microbiota mediates local and systemic lipid metabolism disorders and inflammation • There is a specific link between ileal microbiota, histopathology, and hyperlipidemia.

Selective single-bacteria extraction based on capture and release of microemulsion droplets

Human host-associated microbial communities in body sites can reflect health status based on the population distribution and specific microbial properties in the heterogeneous community. Bacteria identification at the single-cell level provides a reliable biomarker and pathological information for clinical diagnosis. Nevertheless, biosamples obtained from some body sites cannot offer sufficient sample volume and number of target cells as required by most of the existing single-cell isolation methods such as flow cytometry. Herein we report a novel integrated microfluidic system, which consists of a microemulsion module for single-bacteria encapsulation and a sequential microdroplet capture and release module for selectively extracting only the single-bacteria encapsulated in microdroplets. We optimize the system for a success rate of the single-cell extraction to be > 38%. We further verify applicability of the system with prepared cell mixtures (Methylorubrum extorquens AM1 and Methylomicrobium album BG8) and biosamples collected from human skin, to quantify the population distribution of multiple key species in a heterogeneous microbial community. Results indicate perfect viability of the single-cell extracts and compatibility with downstream analyses such as PCR. Together, this research demonstrates that the reported single-bacteria extraction system can be applied in microbiome and pathology research and clinical diagnosis as a clinical or point-of-care device.

Taohong Siwu Decoction promotes the process of fracture healing by activating the VEGF-FAK signal pathway and systemically regulating the gut microbiota

AIMS

This study aimed to explore the effect of Taohong Siwu Decoction (THSWD) on Bone marrow mesenchymal stem cells (BMSCs) at the cellular level and the possible mechanism of systemic regulation of gut microbiota on fracture recovery.

METHODS AND RESULTS

Cell Counting Kit-8 (CCK-8) experiments show that THSWD effectively promotes the proliferation of BMSCs. Transwell and wound healing assays show that THSWD effectively promotes the invasion and migration of BMSCs. Alizarin red staining showed that the THSWD model enhanced the osteogenic differentiation of BMSCs. Moreover, the effect of THSWD on BMSCs is time- and concentration-dependent. RT-qPCR and Western blot results showed that THSWD treatment up-regulated the expression of vascular endothelial growth factor (VEGF) and focal adhesion kinase (FAK) at mRNA and protein levels, respectively. Hematoxylin-eosin and crocin O-quick green staining showed that rats with right femoral shaft fractures, after 14 days of THSWD treatment, the area of callus and cartilage regeneration at the fracture site increased significantly. Gut microbiota was changed in fractured rats, such as the abundance of Bacteroidetes and Firmicutes was increased. THSWD showed positive regulation of both to a certain extent.

CONCLUSION

THSWD up-regulates VEGF and activates the FAK signaling pathway to enhance the development and differentiation of BMSCs, and systematically regulates the gut microbiota to promote fracture healing.

SIGNIFICANCE AND IMPACT OF STUDY

This study provides new insights on the cellular and systemic level to understand the mechanism of THSWD in the treatment of fractures.

Modulated Gut Microbiota for Potential COVID-19 Prevention and Treatment

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has gained global attention. SARS-CoV-2 identifies and invades human cells via angiotensin-converting enzyme 2 receptors, which is highly expressed both in lung tissues and intestinal epithelial cells. The existence of the gut-lung axis in disease could be profoundly important for both disease etiology and treatment. Furthermore, several studies reported that infected patients suffer from gastrointestinal symptoms. The gut microbiota has a noteworthy effect on the intestinal barrier and affects many aspects of human health, including immunity, metabolism, and the prevention of several diseases. This review highlights the function of the gut microbiota in the host's immune response, providing a novel potential strategy through the use of probiotics, gut microbiota metabolites, and dietary products to enhance the gut microbiota as a target for COVID-19 prevention and treatment.

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.

The Roles of the Gut Microbiota and Chronic Low-Grade Inflammation in Older Adults With Frailty

Frailty is a major public issue that affects the physical health and quality of life of older adults, especially as the population ages. Chronic low-grade inflammation has been speculated to accelerate the aging process as well as the development of age-related diseases such as frailty. Intestinal homeostasis plays a crucial role in healthy aging. The interaction between the microbiome and the host regulates the inflammatory response. Emerging evidence indicates that in older adults with frailty, the diversity and composition structure of gut microbiota are altered. Age-associated changes in gut microbiota composition and in their metabolites contribute to increased gut permeability and imbalances in immune function. In this review, we aim to: identify gut microbiota changes in the aging and frail populations; summarize the role of chronic low-grade inflammation in the development of frailty; and outline how gut microbiota may be related to the pathogenesis of frailty, more specifically, in the regulation of gut-derived chronic inflammation. Although additional research is needed, the regulation of gut microbiota may represent a safe, easy, and inexpensive intervention to counteract the chronic inflammation leading to frailty.

Pediatric nonalcoholic fatty liver disease and the microbiome: Mechanisms contributing to pathogenesis and progression

Nonalcoholic fatty liver disease (NAFLD) is the most common form of pediatric liver disease in the United States, and often associated with obesity and metabolic syndrome. NAFLD comprises a broad spectrum of liver diseases, from hepatic steatosis to steatohepatitis, fibrosis and cirrhosis. Disease progression is considered a multi-modal process of liver injury. The intestinal microbiome has been implicated in several aspects of NAFLD pathophysiology. Pediatric studies associating the intestinal microbiome with NAFLD have been limited in number and complicated by inconsistencies in study design and approach. Nevertheless, they provide support for involvement of the intestinal microbiome in NAFLD development and progression and point to common mechanisms shared by microbiome-associated inflammatory diseases with potential to inform future therapeutic intervention.

The Use of Fecal Microbiome Transplant in Treating Human Diseases: Too Early for Poop?

Fecal microbiome transplant (FMT) has gained popularity over the past few years, given its success in treating several gastrointestinal diseases. At the same time, microbial populations in the gut have been shown to have more physiological effects than we expected as "habitants" of the gut. The imbalance in the gut microbiome or dysbiosis, particularly when there are excessive harmful pathogens, can trigger not just infections but can also result in the development of common diseases, such as cancer and cardiometabolic diseases. By using FMT technology, the dysbiosis of the gut microbiome in patients can be resolved by administering fecal materials from a healthy donor. The current review summarizes the history and current uses of FMT before suggesting potential ideas for its high-quality application in clinical settings.

Direct impact of commonly used dietary emulsifiers on human gut microbiota

BACKGROUND

Epidemiologic evidence and animal studies implicate dietary emulsifiers in contributing to the increased prevalence of diseases associated with intestinal inflammation, including inflammatory bowel diseases and metabolic syndrome. Two synthetic emulsifiers in particular, carboxymethylcellulose and polysorbate 80, profoundly impact intestinal microbiota in a manner that promotes gut inflammation and associated disease states. In contrast, the extent to which other food additives with emulsifying properties might impact intestinal microbiota composition and function is not yet known.

METHODS

To help fill this knowledge gap, we examined here the extent to which a human microbiota, maintained ex vivo in the MiniBioReactor Array model, was impacted by 20 different commonly used dietary emulsifiers. Microbiota density, composition, gene expression, and pro-inflammatory potential (bioactive lipopolysaccharide and flagellin) were measured daily.

RESULTS

In accordance with previous studies, both carboxymethylcellulose and polysorbate 80 induced a lasting seemingly detrimental impact on microbiota composition and function. While many of the other 18 additives tested had impacts of similar extent, some, such as lecithin, did not significantly impact microbiota in this model. Particularly stark detrimental impacts were observed in response to various carrageenans and gums, which altered microbiota density, composition, and expression of pro-inflammatory molecules.

CONCLUSIONS

These results indicate that numerous, but not all, commonly used emulsifiers can directly alter gut microbiota in a manner expected to promote intestinal inflammation. Moreover, these data suggest that clinical trials are needed to reduce the usage of the most detrimental compounds in favor of the use of emulsifying agents with no or low impact on the microbiota. Video abstract.

Host/microbiota interactions in health and diseases-Time for mucosal microbiology!

During the last 20 years, a new field of research delineating the importance of the microbiota in health and diseases has emerged. Inappropriate host-microbiota interactions have been shown to trigger a wide range of chronic inflammatory diseases, and defining the exact mechanisms behind perturbations of such relationship, as well as ways by which these disturbances can lead to disease states, both remain to be fully elucidated. The mucosa-associated microbiota constitutes a recently studied microbial population closely linked with the promotion of chronic intestinal inflammation and associated disease states. This review will highlight seminal works that have brought into light the importance of the mucosa-associated microbiota in health and diseases, emphasizing the challenges and promises of expending the mucosal microbiology field of research.

Disruption of small molecule transporter systems by Transporter-Interfering Chemicals (TICs)

Small molecule transporters (SMTs) in the ABC and SLC families are important players in disposition of diverse endo- and xenobiotics. Interactions of environmental chemicals with these transporters were first postulated in the 1990s, and since validated in numerous in vitro and in vivo scenarios. Recent results on the co-crystal structure of ABCB1 with the flame-retardant BDE-100 demonstrate that a diverse range of man-made and natural toxic molecules, hereafter termed transporter-interfering chemicals (TICs), can directly bind to SMTs and interfere with their function. TIC-binding modes mimic those of substrates, inhibitors, modulators, inducers, and possibly stimulants through direct and allosteric mechanisms. Similarly, the effects could directly or indirectly agonize, antagonize or perhaps even prime the SMT system to alter transport function. Importantly, TICs are distinguished from drugs and pharmaceuticals that interact with transporters in that exposure is unintended and inherently variant. Here, we review the molecular mechanisms of environmental chemical interaction with SMTs, the methodological considerations for their evaluation, and the future directions for TIC discovery.

Disruption of the Gut Microbiome Increases the Risk of Periprosthetic Joint Infection in Mice

BACKGROUND

Periprosthetic joint infection (PJI) is one of the most devastating complications of total joint arthroplasty. Given the mortality and morbidity associated with PJI and the challenges in treating it, there has been increased interest in risk factors that can be modified before surgery. In this study, we used a novel mouse model to consider the role of the gut microbiome as a risk factor for PJI.

QUESTIONS/PURPOSES

(1) Does the state of the gut microbiota before surgery influence the likelihood of developing an established infection in a mouse model of PJI? (2) How does the state of the gut microbiota before surgery influence the local and systemic response to the presence of an established infection in a mouse model of PJI?

METHODS

Male C57Bl/6 mice were divided into two groups: those with modified microbiome [INCREMENT]microbiome (n = 40) and untreated mice (n = 42). In [INCREMENT]microbiome mice, the gut flora were modified using oral neomycin and ampicillin from 4 weeks to 16 weeks of age. Mice received a titanium tibial implant to mimic a joint implant and a local inoculation of Staphylococcus aureus in the synovial space (10 colony forming units [CFUs]). The proportion of animals developing an established infection in each group was determined by CFU count. The local and systemic response to established infection was determined using CFU counts in surrounding joint tissues, analysis of gait, radiographs, body weight, serum markers of inflammation, and immune cell profiles and was compared with animals that received the inoculation but resisted infection.

RESULTS

A greater proportion of animals with disrupted gut microbiota had infection (29 of 40 [73%]) than did untreated animals (21 of 42 [50%]; odds ratio, 2.63, 95% CI, 1.04-6.61; p = 0.035). The immune response to established infection in mice with altered microbiota was muted; serum amyloid A, a marker of systemic infection in mice, was greater than in mice with disrupted gut microbiota with infection (689 µg/dL; range, 68-2437 µg/dL, p < 0.05); infection associated increases in monocytes and neutrophils in the spleen and local lymph node in untreated mice but not were not observed in mice with disrupted gut microbiota.

CONCLUSIONS

The findings from this in vivo mouse model suggest that the gut microbiota may influence susceptibility to PJI.

CLINICAL RELEVANCE

These preclinical findings support the idea that the state of the gut microbiome before surgery may influence the development of PJI and justify further preclinical and clinical studies to develop appropriate microbiome-based interventions.

Changes of Intestinal Microecology in Patients with Primary Sjogren's Syndrome after Therapy of Yangyin Yiqi Huoxue Recipe ()

OBJECTIVE

To explore the change of intestinal microecology in patients with primary Sjogren's syndrome (pSS) and correlation with disease activity, and also discuss the therapy effect of Yangyin Yiqi Huoxue Recipe (, YYHD).

METHODS

Sixteen pSS patients were enrolled in the present study, who received 3-month treatment of YYHR, 200 mL orally twice daily. Their pre-and post-test ESSDAI scores, erythrocyte sedimentation rate (ESR) and serum immunoglobulin G (IgG) levels were measured respectively. The 16SrDNA metagenomic sequencing was used to detect and analyze the abundance and diversity of intestinal bacteria flora and the proportion of bacteria at the levels of phylum, family, and genus, in comparision with those of 6 healthy subjects in the control group.

RESULTS

The abundance and diversity of intestinal bacteria flora in pSS patients were lower than those of healthy subjects (P<0.05). After the treatment with YYHD, patients' ESSDAI score and levels of IgG and ESR have decreased significantly (P<0.05). At the phylum level, the proportions of Actinobacteria, Firmicutes, Fusobacteria and Proteobacteria have reduced sharply, while the proportions of Bacteroidetes, Teneriquetes and Candidate-division-TM7 have increased significantly by treatment (all P<0.05). At the classification level, such treatment has caused a significant decrease in the proportions of Bacteroidaceae, Ruminococcaceae, Veillonellaceae, and Enterobacteriacea (all P<0.05), but a significant increase in the proportion of Lachnospiraceae (P<0.05). At the genus level, the treatment has significantly decreased the proportions of Bifidobacterium, Bacteroides, Escherichia-Shigella, Faecalibacterium and Prevotella (all P<0.05), but significantly increased the proportion of Clostridia (P<0.05), close to the levels of healthy subjects (P>0.05).

CONCLUSIONS

There exists an imbalance of intestinal microecology in pSS patients, which can be improved through the treatment with YYHD. Besides, such treatment can also improve the disease activity and adjust the diversity of intestinal bacteria flora, the composition and the abundance of intestinal flora.

Diet Rich in Animal Protein Promotes Pro-inflammatory Macrophage Response and Exacerbates Colitis in Mice

Diet is a major factor determining gut microbiota composition and perturbances in this complex ecosystem are associated with the inflammatory bowel disease (IBD). Here, we used gnotobiotic approach to analyze, how interaction between diet rich in proteins and gut microbiota influences the sensitivity to intestinal inflammation in murine model of ulcerative colitis. We found that diet rich in animal protein (aHPD) exacerbates acute dextran sulfate sodium (DSS)-induced colitis while diet rich in plant protein (pHPD) does not. The deleterious effect of aHPD was also apparent in chronic DSS colitis and was associated with distinct changes in gut bacteria and fungi. Therefore, we induced acute DSS-colitis in germ-free mice and transferred gut microbiota from aCD or aHPD fed mice to find that this effect requires presence of microbes and aHPD at the same time. The aHPD did not change the number of regulatory T cells or Th17 cells and still worsened the colitis in immuno-deficient RAG2 knock-out mice suggesting that this effect was not dependent on adaptive immunity. The pro-inflammatory effect of aHPD was, however, abrogated when splenic macrophages were depleted with clodronate liposomes. This treatment prevented aHPD induced increase in colonic Ly-6C^high pro-inflammatory monocytes, but the ratio of resident Ly-6C^−/low macrophages was not changed. These data show that the interactions between dietary protein of animal origin and gut microbiota increase sensitivity to intestinal inflammation by promoting pro-inflammatory response of monocytes.

Letrozole treatment of adult female mice results in a similar reproductive phenotype but distinct changes in metabolism and the gut microbiome compared to pubertal mice

BACKGROUND

A majority of women with polycystic ovary syndrome (PCOS) have metabolic dysfunction that results in an increased risk of type 2 diabetes. We previously developed a pubertal mouse model using the aromatase inhibitor, letrozole, which recapitulates many of the reproductive and metabolic features of PCOS. To further our understanding of the effects of androgen excess, we compared the effects of letrozole treatment initiated in puberty versus adulthood on reproductive and metabolic phenotypes as well as on the gut microbiome.

RESULTS

Letrozole treatment of both pubertal and adult female mice resulted in reproductive hallmarks of PCOS, including hyperandrogenemia, anovulation and polycystic ovaries. However, unlike pubertal mice, treatment of adult female mice resulted in modest weight gain and abdominal adiposity, minimal elevation in fasting blood glucose and insulin levels, and no detectable insulin resistance. In addition, letrozole treatment of adult mice was associated with a distinct shift in gut microbial diversity compared to letrozole treatment of pubertal mice.

CONCLUSIONS

Our results indicate that dysregulation of metabolism and the gut microbiome in PCOS may be influenced by the timing of androgen exposure. In addition, the minimal weight gain and lack of insulin resistance in adult female mice after letrozole treatment indicates that this model may be useful for investigating the effects of hyperandrogenemia on the hypothalamic-pituitary-gonadal axis and the periphery without the influence of substantial metabolic dysregulation.

Chronic Inflammatory Diseases: Are We Ready for Microbiota-based Dietary Intervention?

The last 15 years have witnessed the emergence of a new field of research that focuses on the roles played by the intestinal microbiota in health and disease. This research field has produced accumulating evidence indicating that dysregulation of host-microbiota interactions contributes to a range of chronic inflammatory diseases, including inflammatory bowel diseases, colorectal cancer, and metabolic syndrome. Although dysregulation of the microbiota can take complex forms, in some cases, specific bacterial species that can drive specific clinical outcomes have been identified. Among the numerous factors influencing the intestinal microbiota composition, diet is a central actor, wherein numerous dietary factors can beneficially or detrimentally impact the host/microbiota relationship. This review will highlight recent literature that has advanced understanding of microbiota-diet-disease interplay, with a central focus on the following question: Are we ready to use intestinal microbiota composition-based personalized dietary interventions to treat chronic inflammatory diseases?

Diet induced changes in the microbiota and cell composition of rabbit gut associated lymphoid tissue (GALT)

The gut associated lymphoid tissue (GALT) is the largest immune organ of the body. Although the gut transient and mucosa-associated microbiota have been largely studied, the microbiota that colonizes the GALT has received less attention. The gut microbiome plays an important role in competitive exclusion of pathogens and in development and maturation of immunity. Diet is a key factor affecting the microbiota composition in the digestive tract. To investigate the relation between diet, microbiota and GALT, microbial and cell composition of vermiform appendix (VA) and sacculus rotundus (SR) were studied in two groups of New Zealand white rabbits on different diets. Diet shifted the lymphoid tissue microbiota affecting the presence and/or absence of certain taxa and their abundances. Immunohistochemistry revealed that a higher fibre content diet resulted in M cell hyperplasia and an increase of recently recruited macrophages, whereas T-cell levels remained unaltered in animals on both high fibre and standard diets. These findings indicate that diet has an impact on the microbiota and cell composition of the GALT, which could act as an important microbial recognition site where interactions with beneficial bacteria can take place favouring microbiota replacement after digestive dysregulations.

Risk assessment of silica nanoparticles on liver injury in metabolic syndrome mice induced by fructose

This study aims to assess the effects and the mechanisms of silica nanoparticles (SiNPs) on hepatotoxicity in both normal and metabolic syndrome mouse models induced by fructose. Here, we found that SiNPs exposure lead to improved insulin resistance in metabolic syndrome mice, but markedly worsened hepatic ballooning, inflammation infiltration, and fibrosis. Moreover, SiNPs exposure aggravated liver injury in metabolic syndrome mice by causing serious DNA damage. Following SiNPs exposure, liver superoxide dismutase and catalase activities in metabolic syndrome mice were stimulated, which is accompanied by significantly increased malondialdehyde and 8-hydroxy-2-deoxyguanosine levels as compared to normal mice. Scanning electron microscope (SEM) revealed that SiNPs were more readily deposited in the liver mitochondria of metabolic syndrome mice, resulting in more severe mitochondrial injury as compared to normal mice. We speculated that SiNPs-induced mitochondrial injury might be the cause of hepatic oxidative stress, which further lead to a series of liver lesions as observed in mice following SiNPs exposure. Based on these results, it is likely that SiNPs will increase the risk and severity of liver disease in individuals with metabolic syndrome. Therefore, SiNPs should be used cautiously in food additives and clinical settings.

Impact of food additives on the gut-brain axis

The mammalian intestinal tract is heavily colonized with a complex community of micro-organisms, present at a very high density, and containing an estimated amount of 10¹⁴ bacteria. The microbiota generally benefits the host, as it plays a central role in maturing the immune system, protecting against infection by entero-pathogens such as Clostridium difficile, and favoring nutrient digestion/energy extraction in our intestine. An altered microbiota, however, can become detrimental and lead to inflammation, metabolic disorders, and even altered behavior/neuroinflammation. While there are many factors involved in regulating the intestinal microbiota composition and the way it interacts with its host, this review will focus on the role played by food additives on host/microbiota relationship.

First victim, later aggressor: How the intestinal microbiota drives the pro-inflammatory effects of dietary emulsifiers?

The intestinal tract is inhabited by a large and diverse community of bacteria, collectively referred to as the gut microbiota. Composed of 500-1000 distinct species, the intestinal microbiota plays an important role in immunity and metabolism. However, alterations in its composition are associated with a variety of inflammatory diseases including obesity, diabetes, and inflammatory bowel disease (IBD). Among many other factors, our diet impacts microbiota composition and function, in either beneficial or detrimental ways. In this addendum, we will discuss our recent findings on how dietary emulsifying agents can directly and detrimentally impact the microbiota, leading to inflammatory diseases and cancer.

Microbiotal-Host Interactions and Hypertension

Hypertension, or elevated blood pressure (BP), has been extensively researched over decades and clearly demonstrated to be caused due to a combination of host genetic and environmental factors. Although much research remains to be conducted to pin-point the precise genetic elements on the host genome that control BP, new lines of evidence are emerging to indicate that, besides the host genome, the genomes of all indigenous commensal micro-organisms, collectively referred to as the microbial metagenome or microbiome, are important, but largely understudied, determinants of BP. Unlike the rigid host genome, the microbiome or the "second genome" can be altered by diet or microbiotal transplantation in the host. This possibility is attractive from the perspective of exploiting the microbiotal composition for clinical management of inherited hypertension. Thus, focusing on the limited current literature supporting a role for the microbiome in BP regulation, this review highlights the need to further explore the role of the co-existence of host and the microbiota as an organized biological unit called the "holobiont" in the context of BP regulation.

Immunologic impact of the intestine in metabolic disease

Obesity and diabetes are associated with increased chronic low-grade inflammation and elevated plasma glucose levels. Although inflammation in the fat and liver are established features of obesity-associated insulin resistance, the intestine is emerging as a new site for immunologic changes that affect whole-body metabolism. Specifically, microbial and dietary factors incurred by diet-induced obesity influence underlying innate and adaptive responses of the intestinal immune system. These responses affect the maintenance of the intestinal barrier, systemic inflammation, and glucose metabolism. In this Review we propose that an understanding of the changes to the intestinal immune system, and how these changes influence systemic immunity and glucose metabolism in a whole-body integrative and a neuronal-dependent network, will unveil novel intestinal pathologic and therapeutic targets for diabetes and obesity.

Gut Homeostasis, Microbial Dysbiosis, and Opioids

Gut homeostasis plays an important role in maintaining animal and human health. The disruption of gut homeostasis has been shown to be associated with multiple diseases. The mutually beneficial relationship between the gut microbiota and the host has been demonstrated to maintain homeostasis of the mucosal immunity and preserve the integrity of the gut epithelial barrier. Currently, rapid progress in the understanding of the host-microbial interaction has redefined toxicological pathology of opioids and their pharmacokinetics. However, it is unclear how opioids modulate the gut microbiome and metabolome. Our study, showing opioid modulation of gut homeostasis in mice, suggests that medical interventions to ameliorate the consequences of drug use/abuse will provide potential therapeutic and diagnostic strategies for opioid-modulated intestinal infections. The study of morphine's modulation of the gut microbiome and metabolome will shed light on the toxicological pathology of opioids and its role in the susceptibility to infectious diseases.

Links Between the Microbiome and Bone

The human microbiome has been shown to influence a number of chronic conditions associated with impaired bone mass and bone quality, including obesity, diabetes, and inflammatory bowel disease. The connection between the microbiome and bone health, however, has not been well studied. The few studies available demonstrate that the microbiome can have a large effect on bone remodeling and bone mass. The gut microbiome is the largest reservoir of microbial organisms in the body and consists of more than a thousand different species interacting with one another in a stable, dynamic equilibrium. How the microbiome can affect organs distant from the gut is not well understood but is believed to occur through regulation of nutrition, regulation of the immune system, and/or translocation of bacterial products across the gut endothelial barrier. Here we review each of these mechanisms and discuss their potential effect on bone remodeling and bone mass. We discuss how preclinical studies of bone-microbiome interactions are challenging because the microbiome is sensitive to genetic background, housing environment, and vendor source. Additionally, although the microbiome exhibits a robust response to external stimuli, it rapidly returns to its original steady state after a disturbance, making it difficult to sustain controlled changes in the microbiome over time periods required to detect alterations in bone remodeling, mass, or structure. Despite these challenges, an understanding of the mechanisms by which the gut microbiome affects bone has the potential to provide insights into the dissociation between fracture risk and bone mineral density in patients including those with obesity, diabetes, or inflammatory bowel disease. In addition, alteration of the gut microbiome has the potential to serve as a biomarker of bone metabolic activity as well as a target for therapies to improve bone structure and quality using pharmaceutical agents or pre- or probiotics. © 2016 American Society for Bone and Mineral Research.

Mycobacterium avium Subspecies paratuberculosis Infection Modifies Gut Microbiota under Different Dietary Conditions in a Rabbit Model

Mycobacterium avium subspecies paratuberculosis (MAP) the causative agent of paratuberculosis, produces a chronic granulomatous inflammation of the gastrointestinal tract of ruminants. It has been recently suggested that MAP infection may be associated with dysbiosis of intestinal microbiota in ruminants. Since diet is one of the key factors affecting the balance of microbial populations in the digestive tract, we intended to evaluate the effect of MAP infection in a rabbit model fed a regular or high fiber diet during challenge. The composition of microbiota of the cecal content and the sacculus rotundus was studied in 20 New Zealand white female rabbits. The extracted DNA was subjected to paired-end Illumina sequencing of the V3-V4 hypervariable region of the 16S rRNA gene for microbiota analysis. Microbial richness (Chao1) in the cecal content was significantly increased by MAP infection in regular diet rabbits (p = 0.0043) and marginally increased (p = 0.0503) in the high fiber group. Analysis of beta-diversity showed that MAP infection produces deeper changes in the microbiota of sacculus rotundus than in the cecal content. A lower abundance of Proteobacteria in the cecal content of infected animals fed the high fiber diet and also lower abundance of Bacteroidetes in the sacculus rotundus of infected animals fed the regular diet were observed. Based on OPLS-DA analysis, we observed that some bacteria repeatedly appear to be positively associated with infection in different samples under different diets (families Dehalobacteriaceae, Coriobacteriaceae, and Mogibacteriaceae; genus Anaerofustis). The same phenomenon was observed with some of the bacteria negatively associated with MAP infection (genera Anaerostipes and Coprobacillus). However, other groups of bacteria (Enterobacteriaceae family and ML615J-28 order) were positively associated with infection in some circumstances and negatively associated with infection in others. Data demonstrate that MAP infection and diet changes do interact and result in shifts in the microbiota of the cecal content and sacculus rotundus of rabbits.

The Gut Microbiome Is Altered in a Letrozole-Induced Mouse Model of Polycystic Ovary Syndrome

Women with polycystic ovary syndrome (PCOS) have reproductive and metabolic abnormalities that result in an increased risk of infertility, diabetes and cardiovascular disease. The large intestine contains a complex community of microorganisms (the gut microbiome) that is dysregulated in humans with obesity and type 2 diabetes. Using a letrozole-induced PCOS mouse model, we demonstrated significant diet-independent changes in the gut microbial community, suggesting that gut microbiome dysbiosis may also occur in PCOS women. Letrozole treatment was associated with a time-dependent shift in the gut microbiome and a substantial reduction in overall species and phylogenetic richness. Letrozole treatment also correlated with significant changes in the abundance of specific Bacteroidetes and Firmicutes previously implicated in other mouse models of metabolic disease in a time-dependent manner. Our results suggest that the hyperandrogenemia observed in PCOS may significantly alter the gut microbiome independently of diet.

Mammalian gut immunity

The mammalian intestinal tract is the largest immune organ in the body and comprises cells from non-hemopoietic (epithelia, Paneth cells, goblet cells) and hemopoietic (macrophages, dendritic cells, T-cells) origin, and is also a dwelling for trillions of microbes collectively known as the microbiota. The homeostasis of this large microbial biomass is prerequisite to maintain host health by maximizing beneficial symbiotic relationships and minimizing the risks of living in such close proximity. Both microbiota and host immune system communicate with each other to mutually maintain homeostasis in what could be called a "love-hate relationship." Further, the host innate and adaptive immune arms of the immune system cooperate and compensate each other to maintain the equilibrium of a highly complex gut ecosystem in a stable and stringent fashion. Any imbalance due to innate or adaptive immune deficiency or aberrant immune response may lead to dysbiosis and low-grade to robust gut inflammation, finally resulting in metabolic diseases.

Evidence for a link between gut microbiota and hypertension in the Dahl rat

The gut microbiota plays a critical role in maintaining physiological homeostasis. This study was designed to evaluate whether gut microbial composition affects hypertension. 16S rRNA genes obtained from cecal samples of Dahl salt-sensitive (S) and Dahl salt-resistant (R) rats were sequenced. Bacteria of the phylum Bacteroidetes were higher in the S rats compared with the R rats. Furthermore, the family S24-7 of the phylum Bacteroidetes and the family Veillonellaceae of the phylum Firmicutes were higher in the S rats compared with the R rats. Analyses of the various phylogenetic groups of cecal microbiota revealed significant differences between S and R rats. Both strains were maintained on a high-salt diet, administered antibiotics for ablation of microbiota, transplanted with S or R rat cecal contents, and monitored for blood pressure (BP). Systolic BP of the R rats remained unaltered irrespective of S or R rat cecal transplantation. Surprisingly, compared with the S rats given S rat cecal content, systolic BP of the S rats given a single bolus of cecal content from R rats was consistently and significantly elevated during the rest of their life, and they had a shorter lifespan. A lower level of fecal bacteria of the family Veillonellaceae and increased plasma acetate and heptanoate were features associated with the increased BP observed in the S rats given R rat microbiota compared with the S rats given S rat microbiota. These data demonstrate a link between microbial content and BP regulation and, because the S and R rats differ in their genomic composition, provide the necessary basis to further examine the relationship between the host genome and microbiome in the context of BP regulation in the Dahl rats.

Intestinal microbiome and lymphoma development

The intestinal microbiota and gut immune system must communicate to maintain a balance between tolerance and activation. Our immune system protects us from pathogenic microbes at the same time that our bodies are host to trillions of microbes, symbionts, mutualists, and some that are essential to human health. Since there is such a close interaction between the immune system and the intestinal microbiota, it is not surprising that some lymphomas such as mucosal-associated lymphoid tissue lymphoma have been shown to be caused by the presence of certain bacteria. Animal models have played an important role in elucidating the causation and establishing the mechanism of bacteria-induced mucosal-associated lymphoid tissue lymphoma. In this review, we discuss different ways that animal models have been applied to investigate links between the gut microbiota and lymphoma and have helped to reveal the mechanisms of microbiota-induced lymphoma. Although there is a paucity of published studies demonstrating the interplay between the microbiota and lymphoma development, we believe that the connection is real and that it can be exploited in the future to enhance our understanding of causation and to improve the prognosis and treatment of lymphoma.

Growth and metastasis of B16-F10 melanoma cells is not critically dependent on host CD73 expression in mice

Background

Recent studies have suggested that adenosine generated by ecto-5′-nucleotidase (CD73) in the tumor microenvironment plays a major role in promoting tumor growth by suppressing the immune response and stimulating angiogenesis via A2A and A2B receptors. However, adenosine has also been reported to inhibit tumor growth acting via A1 and A3 receptors. Therefore the aim of this study was to clarify the role of host CD73, which catalyzes the extracellular hydrolysis of AMP to adenosine, on tumor growth and metastasis of B16-F10 melanoma cells.

Methods

CD73 and alkaline phosphatase (AP) activity of B16-F10 melanoma cells were measured by HPLC. Tumor cells were injected either subcutaneously or intradermally in WT and CD73^−/− mice and tumor growth was monitored by MRI at 9.4 T. Immune cell subpopulations within tumors were assessed by FACS after enzymatic digestion. An endothelium specific CD73^−/− was created using Tie2-Cre⁺ mice and CD73^flox/flox (loxP) mice. Chimeric mice lacking CD73^−/− on hematopoietic cells was generated by bone marrow transplantation. Lung metastatic spread was measured after intravenous B16-F10 application.

Results

B16-F10 cells showed very little CD73 and negligible AP activity. Neither complete loss of host CD73 nor specific knockout of CD73 on endothelial cells or hematopoietic cells affected tumor growth after subcutaneous or intradermal tumor cell application. Only peritumoral edema formation was significantly attenuated in global CD73^−/− mice in the intradermal model. Immune cell composition revealed no differences in the different transgenic mice models. Also lung metastasis after intravenous B16-F10 injection was not altered in CD73^−/− mice.

Conclusions

CD73 expression on host cells, particularly on endothelial and hematopoietic cells, does not modulate tumor growth and metastatic spread of B16-F10 melanoma cells most likely because of insufficient adenosine formation by the tumor itself.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-898) contains supplementary material, which is available to authorized users.

Conducting a microbiome study

Human microbiome research is an actively developing area of inquiry, with ramifications for our lifestyles, our interactions with microbes, and how we treat disease. Advances depend on carefully executed, controlled, and reproducible studies. Here, we provide a Primer for researchers from diverse disciplines interested in conducting microbiome research. We discuss factors to be considered in the design, execution, and data analysis of microbiome studies. These recommendations should help researchers to enter and contribute to this rapidly developing field.

Lymphoma caused by intestinal microbiota

The intestinal microbiota and gut immune system must constantly communicate to maintain a balance between tolerance and activation: on the one hand, our immune system should protect us from pathogenic microbes and on the other hand, most of the millions of microbes in and on our body are innocuous symbionts and some can even be beneficial. Since there is such a close interaction between the immune system and the intestinal microbiota, it is not surprising that some lymphomas such as mucosal-associated lymphoid tissue (MALT) lymphoma have been shown to be caused by the presence of certain bacteria. Animal models played an important role in establishing causation and mechanism of bacteria-induced MALT lymphoma. In this review we discuss different ways that animal models have been applied to establish a link between the gut microbiota and lymphoma and how animal models have helped to elucidate mechanisms of microbiota-induced lymphoma. While there are not a plethora of studies demonstrating a connection between microbiota and lymphoma development, we believe that animal models are a system which can be exploited in the future to enhance our understanding of causation and improve prognosis and treatment of lymphoma.

MAP3K8 (TPL2/COT) affects obesity-induced adipose tissue inflammation without systemic effects in humans and in mice

Chronic low-grade inflammation in adipose tissue often accompanies obesity, leading to insulin resistance and increasing the risk for metabolic diseases. MAP3K8 (TPL2/COT) is an important signal transductor and activator of pro-inflammatory pathways that has been linked to obesity-induced adipose tissue inflammation. We used human adipose tissue biopsies to study the relationship of MAP3K8 expression with markers of obesity and expression of pro-inflammatory cytokines (IL-1β, IL-6 and IL-8). Moreover, we evaluated obesity-induced adipose tissue inflammation and insulin resistance in mice lacking MAP3K8 and WT mice on a high-fat diet (HFD) for 16 weeks. Individuals with a BMI >30 displayed a higher mRNA expression of MAP3K8 in adipose tissue compared to individuals with a normal BMI. Additionally, high mRNA expression levels of IL-1β, IL-6 and IL-8, but not TNF -α, in human adipose tissue were associated with higher expression of MAP3K8. Moreover, high plasma SAA and CRP did not associate with increased MAP3K8 expression in adipose tissue. Similarly, no association was found for MAP3K8 expression with plasma insulin or glucose levels. Mice lacking MAP3K8 had similar bodyweight gain as WT mice, yet displayed lower mRNA expression levels of IL-1β, IL-6 and CXCL1 in adipose tissue in response to the HFD as compared to WT animals. However, MAP3K8 deficient mice were not protected against HFD-induced adipose tissue macrophage infiltration or the development of insulin resistance. Together, the data in both human and mouse show that MAP3K8 is involved in local adipose tissue inflammation, specifically for IL-1β and its responsive cytokines IL-6 and IL-8, but does not seem to have systemic effects on insulin resistance.