Maternal cecal microbiota transfer rescues early-life antibiotic-induced enhancement of type 1 diabetes in mice

Can fecal microbiota transplantations modulate autoimmune responses in type 1 diabetes?

Type 1 diabetes (T1D) is a chronic autoimmune disease targeting insulin-producing pancreatic beta cells. T1D is a multifactorial disease incorporating genetic and environmental factors. In recent years, the advances in high-throughput sequencing have allowed researchers to elucidate the changes in the gut microbiota taxonomy and functional capacity that accompany T1D development. An increasing number of studies have shown a role of the gut microbiota in mediating immune responses in health and disease, including autoimmunity. Fecal microbiota transplantations (FMT) have been largely used in murine models to prove a causal role of the gut microbiome in disease progression and have been shown to be a safe and effective treatment in inflammatory human diseases. In this review, we summarize and discuss recent research regarding the gut microbiota-host interactions in T1D, the current advancement in therapies for T1D, and the usefulness of FMT studies to explore microbiota-host immunity encounters in murine models and to shape the course of human type 1 diabetes.

Predicting the role of the human gut microbiome in type 1 diabetes using machine-learning methods

Gut microbes is a crucial factor in the pathogenesis of type 1 diabetes (T1D). However, it is still unclear which gut microbiota are the key factors affecting T1D and their influence on the development and progression of the disease. To fill these knowledge gaps, we constructed a model to find biomarker from gut microbiota in patients with T1D. We first identified microbial markers using Linear discriminant analysis Effect Size (LEfSe) and random forest (RF) methods. Furthermore, by constructing co-occurrence networks for gut microbes in T1D, we aimed to reveal all gut microbial interactions as well as major beneficial and pathogenic bacteria in healthy populations and type 1 diabetic patients. Finally, PICRUST2 was used to predict Kyoto Encyclopedia of Genes and Genomes (KEGG) functional pathways and KO gene levels of microbial markers to investigate the biological role. Our study revealed that 21 identified microbial genera are important biomarker for T1D. Their AUC values are 0.962 and 0.745 on discovery set and validation set. Functional analysis showed that 10 microbial genera were significantly positively associated with D-arginine and D-ornithine metabolism, spliceosome in transcription, steroid hormone biosynthesis and glycosaminoglycan degradation. These genera were significantly negatively correlated with steroid biosynthesis, cyanoamino acid metabolism and drug metabolism. The other 11 genera displayed an inverse correlation. In summary, our research identified a comprehensive set of T1D gut biomarkers with universal applicability and have revealed the biological consequences of alterations in gut microbiota and their interplay. These findings offer significant prospects for individualized management and treatment of T1D.

Advances in regulation of homeostasis through chromatin modifications by airway commensals

Commensal bacteria are residents of the human airway where they interact with both colonizing pathogens and host respiratory epithelial cells of this mucosal surface. It is here that commensals exert their influence through host signaling cascades, host transcriptional responses and host immunity, all of which are rooted in chromatin remodeling and histone modifications. Recent studies show that airway commensals impact host chromatin, but compared the what is known for gut commensals, the field remains in its infancy. The mechanisms by which airway commensals regulate respiratory health and homeostasis through chromatin modifications is of increasing interest, specifically since their displacement precedes the increased potential for respiratory disease. Herein we will discuss recent advances and intriguing avenues of future work aimed at deciphering how airway commensals protect and influence respiratory health.

Microbial-Derived Exerkines Prevent Skeletal Muscle Atrophy

Regular exercise yields a multitude of systemic benefits, many of which may be mediated through the gut microbiome. Here, we report that cecal microbial transplants (CMTs) from exercise-trained vs. sedentary mice have modest benefits in reducing skeletal muscle atrophy using a mouse model of unilaterally hindlimb-immobilization. Direct administration of top microbial-derived exerkines from an exercise-trained gut microbiome preserved muscle function and prevented skeletal muscle atrophy.

The Microbiome and Infectious Diseases

Our perception of microbes has considerably changed since the recognition of their pathogenic potential in the 19th century. The discovery of antibiotics and their subsequent widespread adoption have substantially altered the landscape of medicine, providing us with treatment options for many infectious diseases and enabling the deployment of previously risky interventions (eg, surgical procedures and chemotherapy), while also leading to the rise of AMR. The latter is commonly viewed as the predominant downside of antibiotic use. However, with the increasing recognition that all metazoan organisms rely on a community of microbes (the microbiota) for normal development and for most physiologic processes, the negative impacts of antibiotic use now extend well beyond AMR. Using the iceberg as a metaphor, we argue that the effects of antibiotics on AMR represent the tip of the iceberg, with much greater repercussions stemming from their role in the rise of so-called noncommunicable diseases (including obesity, diabetes, allergic and autoimmune diseases, neurodevelopmental disorders, and certain cancers). We highlight some of the emerging science around the intersection of the microbiome, antibiotic use, and health (including biological costs and future therapeutic avenues), and we advocate a more nuanced approach in evaluating the impacts of proposed antibiotic use, especially in the setting of preexposure and postexposure prophylaxis.

Gut Microbiota Is Associated with Onset and Severity of Type 1 Diabetes in Nonobese Diabetic Mice Treated with Anti-PD-1

Our bodies are home to individual-specific microbial ecosystems that have recently been found to be modified by cancer immunotherapies. The interaction between the gut microbiome and islet autoimmunity leading to type I diabetes (T1D) is well described and highlights the microbiome contribution during the onset and T1D development in animals and humans. As cancer immunotherapies induce gut microbiome perturbations and immune-mediated adverse events in susceptible patients, we hypothesized that NOD mice can be used as a predictive tool to investigate the effects of anti-PD-1 treatment on the onset and severity of T1D, and how microbiota influences immunopathology. In this longitudinal study, we showed that anti-PD-1 accelerated T1D onset, increased glutamic acid decarboxylase-reactive T cell frequency in spleen, and precipitated destruction of β cells, triggering high glucose levels and pancreatic islet reduction. Anti-PD-1 treatment also resulted in temporal microbiota changes and lower diversity characteristic of T1D. Finally, we identified known insulin-resistance regulating bacteria that were negatively correlated with glucose levels, indicating that anti-PD-1 treatment impacts the early gut microbiota composition. Moreover, an increase of mucin-degrading Akkermansia muciniphila points to alterations of barrier function and immune system activation. These results highlight the ability of microbiota to readily respond to therapy-triggered pathophysiological changes as rescuers (Bacteroides acidifaciens and Parabacteroides goldsteinii) or potential exacerbators (A. muciniphila). Microbiome-modulating interventions may thus be promising mitigation strategies for immunotherapies with high risk of immune-mediated adverse events.

Gut bacteria induce IgA expression in pituitary hormone-secreting cells during aging

Pituitary hormone decline is a hallmark of aging. However, the precise gene regulation mechanism during pituitary aging is unclear. Here, we characterized the cell population alteration and global transcriptional change during pituitary aging through single-cell RNA sequencing (scRNA-seq). We found that mRNA-encoding components of protein translational machinery declined the most in the pituitary during aging. Remarkably, Immunoglobulin A (IgA) was found to be expressed in hormone-secreting cells, and the IgA expression level increased dramatically in aged pituitary. Moreover, the pituitary IgA expression was regulated by gut microbiota. The non-hematopoietic origin of the IgA+ cells in the pituitary was further confirmed through bone marrow transplantation. Somatotropes were identified as the most prominent IgA-producing cells through lineage tracing. Thus, pituitary hormone-secreting cells can generate IgA in an age-dependent manner, and such a process is influenced by gut bacteria.

Select symbionts drive high IgA levels in the mouse intestine

Immunoglobulin A (IgA) is an important factor in maintaining homeostasis at mucosal surfaces, yet luminal IgA levels vary widely. Total IgA levels are thought to be driven by individual immune responses to specific microbes. Here, we found that the prebiotic, pectin oligosaccharide (pec-oligo), induced high IgA levels in the small intestine in a T cell-dependent manner. Surprisingly, this IgA-high phenotype was retained after cessation of pec-oligo treatment, and microbiome transmission either horizontally or vertically was sufficient to retain high IgA levels in the absence of pec-oligo. Interestingly, the bacterial taxa enriched in the overall pec-oligo bacterial community differed from IgA-coated microbes in this same community. Rather, a group of ethanol-resistant microbes, highly enriched for Lachnospiraceae bacterium A2, drove the IgA-high phenotype. These findings support a model of intestinal adaptive immunity in which a limited number of microbes can promote durable changes in IgA directed to many symbionts.

The microbiota of pregnant women with SARS-CoV-2 and their infants

BACKGROUND

Infants receive their first bacteria from their birthing parent. This newly acquired microbiome plays a pivotal role in developing a robust immune system, the cornerstone of long-term health.

RESULTS

We demonstrated that the gut, vaginal, and oral microbial diversity of pregnant women with SARS-CoV-2 infection is reduced, and women with early infections exhibit a different vaginal microbiota composition at the time of delivery compared to their healthy control counterparts. Accordingly, a low relative abundance of two Streptococcus sequence variants (SV) was predictive of infants born to pregnant women with SARS-CoV-2 infection.

CONCLUSIONS

Our data suggest that SARS-CoV-2 infections during pregnancy, particularly early infections, are associated with lasting changes in the microbiome of pregnant women, compromising the initial microbial seed of their infant. Our results highlight the importance of further exploring the impact of SARS-CoV-2 on the infant's microbiome-dependent immune programming. Video Abstract.

Disruption of the early-life microbiota alters Peyer's patch development and germinal center formation in gastrointestinal-associated lymphoid tissue

During postnatal development, both the maturing microbiome and the host immune system are susceptible to environmental perturbations such as antibiotic use. The impact of timing in which antibiotic exposure occurs was investigated by treating mice from days 5-9 with amoxicillin or azithromycin, two of the most commonly prescribed medications in children. Both early-life antibiotic regimens disrupted Peyer's patch development and immune cell abundance, with a sustained decrease in germinal center formation and diminished intestinal immunoglobulin A (IgA) production. These effects were less pronounced in adult mice. Through comparative analysis of microbial taxa, Bifidobacterium longum abundance was found to be associated with germinal center frequency. When re-introduced to antibiotic-exposed mice, B. longum partially rescued the immunological deficits. These findings suggest that early-life antibiotic use affects the development of intestinal IgA-producing B cell functions and that probiotic strains could be used to restore normal development after antibiotic exposure.

Serum amyloid A and metabolic disease: evidence for a critical role in chronic inflammatory conditions

Serum amyloid A (SAA) subtypes 1-3 are well-described acute phase reactants that are elevated in acute inflammatory conditions such as infection, tissue injury, and trauma, while SAA4 is constitutively expressed. SAA subtypes also have been implicated as playing roles in chronic metabolic diseases including obesity, diabetes, and cardiovascular disease, and possibly in autoimmune diseases such as systemic lupus erythematosis, rheumatoid arthritis, and inflammatory bowel disease. Distinctions between the expression kinetics of SAA in acute inflammatory responses and chronic disease states suggest the potential for differentiating SAA functions. Although circulating SAA levels can rise up to 1,000-fold during an acute inflammatory event, elevations are more modest (∼5-fold) in chronic metabolic conditions. The majority of acute-phase SAA derives from the liver, while in chronic inflammatory conditions SAA also derives from adipose tissue, the intestine, and elsewhere. In this review, roles for SAA subtypes in chronic metabolic disease states are contrasted to current knowledge about acute phase SAA. Investigations show distinct differences between SAA expression and function in human and animal models of metabolic disease, as well as sexual dimorphism of SAA subtype responses.

An interplay between non-coding RNAs and gut microbiota in human health

Humans have a complicated symbiotic relationship with their gut microbiome, which is postulated to impact host health and disease broadly. Epigenetic alterations allow host cells to regulate gene expression without altering the DNA sequence. The gut microbiome, offering environmental hints, can influence responses to stimuli by host cells with modifications on their epigenome and gene expression. Recent increasing data suggest that regulatory non-coding RNAs (miRNAs, circular RNAs, and long lncRNA) may affect host-microbe interactions. These RNAs have been suggested as potential host response biomarkers in microbiome-associated disorders, including diabetes and cancer. This article reviews the current understanding of the interplay between gut microbiota and non-coding RNA, including lncRNA, miRNA, and circular RNA. This can lead to a profound understanding of human disease and influence therapy. Furthermore, microbiome engineering as a mainstream strategy for improving human health has been discussed and confirms the hypothesis about a direct cross-talk between microbiome composition and non-coding RNA.

Gut microbiota in COVID-19: key microbial changes, potential mechanisms and clinical applications

The gastrointestinal tract is involved in coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The gut microbiota has important roles in viral entry receptor angiotensin-converting enzyme 2 (ACE2) expression, immune homeostasis, and crosstalk between the gut and lungs, the 'gut-lung axis'. Emerging preclinical and clinical studies indicate that the gut microbiota might contribute to COVID-19 pathogenesis and disease outcomes; SARS-CoV-2 infection was associated with altered intestinal microbiota and correlated with inflammatory and immune responses. Here, we discuss the cutting-edge evidence on the interactions between SARS-CoV-2 infection and the gut microbiota, key microbial changes in relation to COVID-19 severity and host immune dysregulations with the possible underlying mechanisms, and the conceivable consequences of the pandemic on the human microbiome and post-pandemic health. Finally, potential modulatory strategies of the gut microbiota are discussed. These insights could shed light on the development of microbiota-based interventions for COVID-19.

Programmed and environmental determinants driving neonatal mucosal immune development

The mucosal immune system of neonates goes through successive, non-redundant phases that support the developmental needs of the infant and ultimately establish immune homeostasis. These phases are informed by environmental cues, including dietary and microbial stimuli, but also evolutionary developmental programming that functions independently of external stimuli. The immune response to exogenous stimuli is tightly regulated during early life; thresholds are set within this neonatal "window of opportunity" that govern how the immune system will respond to diet, the microbiota, and pathogenic microorganisms in the future. Thus, changes in early-life exposure, such as breastfeeding or environmental and microbial stimuli, influence immunological and metabolic homeostasis and the risk of developing diseases such as asthma/allergy and obesity.

The gut microbiota pathway mechanisms of diabetes

The contribution of dysbiotic gut microbiota configuration is essential when making reference to the metabolic disorders by increasing energy. It is important to understand that the gut microbiota induced metabolic disease mechanisms and inflammations. Thus it is imperative to have an insight into the state of all chronic subclinical inflammations influencing disease outcomes. However, from the emerging studies, there still exist inconsistencies in the findings of such studies. While making the best out of the reasons for inconsistencies of the findings, this review is designed to make a clear spell out as to the inconsistence of gut microbiota with respect to diabetes. It considered gut-virome alterations and diabetes and gut-bacteriome-gut-virome-alterations and diabetes as confounding factors. The review further explained some study design strategies that will spontaneously eliminate any potential confounding factors to lead to a more evidence based diabetic-gut microbiota medicine. Lipopolysaccharide (LPS) pro-inflammatory, metabolic endotoxemia and diet/gut microbiota insulin-resistance and low-grade systemic inflammation induced by gut microbiota can trigger pro-inflammatory cytokines in insulin-resistance, consequently, leading to the diabetic condition. While diet influences the gut microbiota, the consequences are mainly the constant high levels of pro-inflammatory cytokines in the circulatory system. Of recent, dietary natural products have been shown to be anti-diabetic. The effects of resveratrol on the gut showed an improved lipid profile, anti-inflammatory properties and ameliorated the endotoxemia, tight junction and glucose intolerance.

Antibiotics in the pathogenesis of diabetes and inflammatory diseases of the gastrointestinal tract

Antibiotic use is increasing worldwide. However, the use of antibiotics is clearly associated with changes in gut microbiome composition and function, and perturbations have been identified as potential environmental risk factors for chronic inflammatory disorders of the gastrointestinal tract. In this Review, we examine the association between the use of antibiotics and the onset and development of both type 1 and type 2 diabetes, inflammatory bowel disease, including ulcerative colitis and Crohn's disease, as well as coeliac disease and eosinophilic oesophagitis. We discuss the key findings of epidemiological studies, provide mechanistic insights into the pathways by which the gut microbiota might contribute to these diseases, and assess clinical trials investigating the effects of antibiotics. Such studies indicate that antibiotic exposures, varying in type, timing and dosage, could explain differences in disease risk. There seems to be a critical window in early life in which perturbation of the microbiome has a substantial effect on disease development. Identifying the antibiotic-perturbed gut microbiota as a factor that contributes to the pathophysiology of these inflammatory disorders might stimulate new approaches to prevention, diagnosis and treatment.

Gut microbiome in type 1 diabetes: the immunological perspective

INTRODUCTION

Type 1 diabetes (T1D) is a prevalent, and yet uncurable, autoimmune disease targeting insulin-producing pancreatic β-cells. Despite a known genetic component in T1D onset, genetics alone cannot explain the alarming worldwide rise in T1D incidence, which is attributed to a growing impact of environmental factors, including perturbations of the gut microbiome.

AREAS COVERED

Intestinal commensal bacteria plays a crucial role in host physiology in health and disease by regulating endocrine and immune functions. An aberrant gut microbiome structure and metabolic function have been documented prior and during T1D onset. In this review, we summarize and discuss the current studies depicting the taxonomic profile and role of the gut microbial communities in murine models of T1D, diabetic patients and human interventional trials.

EXPERT OPINION

Compelling evidence have shown that the intestinal microbiota is instrumental in driving differentiation and functions of immune cells. Therefore, any alterations in the intestinal microbiome composition or microbial metabolite production, particularly early in life, may impact disease susceptibility and amplify inflammatory responses and hence accelerate the course of T1D pathogenesis.

BefA, a microbiota-secreted membrane disrupter, disseminates to the pancreas and increases β cell mass

Microbiome dysbiosis is a feature of diabetes, but how microbial products influence insulin production is poorly understood. We report the mechanism of BefA, a microbiome-derived protein that increases proliferation of insulin-producing β cells during development in gnotobiotic zebrafish and mice. BefA disseminates systemically by multiple anatomic routes to act directly on pancreatic islets. We detail BefA's atomic structure, containing a lipid-binding SYLF domain, and demonstrate that it permeabilizes synthetic liposomes and bacterial membranes. A BefA mutant impaired in membrane disruption fails to expand β cells, whereas the pore-forming host defense protein, Reg3, stimulates β cell proliferation. Our work demonstrates that membrane permeabilization by microbiome-derived and host defense proteins is necessary and sufficient for β cell expansion during pancreas development, potentially connecting microbiome composition with diabetes risk.

Functional and metabolic alterations of gut microbiota in children with new-onset type 1 diabetes

Gut dysbiosis has been linked to type 1 diabetes (T1D); however, microbial capacity in T1D remains unclear. Here, we integratively profiled gut microbial functional and metabolic alterations in children with new-onset T1D in independent cohorts and investigated the underlying mechanisms. In T1D, the microbiota was characterized by decreased butyrate production and bile acid metabolism and increased lipopolysaccharide biosynthesis at the species, gene, and metabolite levels. The combination of 18 bacterial species and fecal metabolites provided excellently discriminatory power for T1D. Gut microbiota from children with T1D induced elevated fasting glucose levels and declined insulin sensitivity in antibiotic-treated mice. In streptozotocin-induced T1D mice, butyrate and lipopolysaccharide exerted protective and destructive effects on islet structure and function, respectively. Lipopolysaccharide aggravated the pancreatic inflammatory response, while butyrate activated Insulin1 and Insulin2 gene expression. Our study revealed perturbed microbial functional and metabolic traits in T1D, providing potential avenues for microbiome-based prevention and intervention for T1D.

The role of the gut microbiota in health and cardiovascular diseases

The gut microbiota is critical to human health, such as digesting nutrients, forming the intestinal epithelial barrier, regulating immune function, producing vitamins and hormones, and producing metabolites to interact with the host. Meanwhile, increasing evidence indicates that the gut microbiota has a strong correlation with the occurrence, progression and treatment of cardiovascular diseases (CVDs). In patients with CVDs and corresponding risk factors, the composition and ratio of gut microbiota have significant differences compared with their healthy counterparts. Therefore, gut microbiota dysbiosis, gut microbiota-generated metabolites, and the related signaling pathway may serve as explanations for some of the mechanisms about the occurrence and development of CVDs. Several studies have also demonstrated that many traditional and latest therapeutic treatments of CVDs are associated with the gut microbiota and its generated metabolites and related signaling pathways. Given that information, we summarized the latest advances in the current research regarding the effect of gut microbiota on health, the main cardiovascular risk factors, and CVDs, highlighted the roles and mechanisms of several metabolites, and introduced corresponding promising treatments for CVDs regarding the gut microbiota. Therefore, this review mainly focuses on exploring the role of gut microbiota related metabolites and their therapeutic potential in CVDs, which may eventually provide better solutions in the development of therapeutic treatment as well as the prevention of CVDs.

Global trends in research on miRNA–microbiome interaction from 2011 to 2021: A bibliometric analysis

An increasing number of research suggests that the microRNA (miRNA)–microbiome interaction plays an essential role in host health and diseases. This bibliometric analysis aimed to identify the status of global scientific output, research hotspots, and frontiers regarding the study of miRNA–microbiome interaction over the past decade. We retrieved miRNA–microbiome-related studies published from 2011 to 2021 from the Web of Science Core Collection database; the R package bibliometrix was used to analyze bibliometric indicators, and VOSviewer was used to visualize the field status, hotspots, and research trends of miRNA–microbiome interplay. In total, 590 articles and reviews were collected. A visual analysis of the results showed that significant increase in the number of publications over time. China produced the most papers, and the United States contributed the highest number of citations. Shanghai Jiaotong University and the University of California Davis were the most active institutions in the field. Most publications were published in the areas of biochemistry and molecular biology. Yu Aiming was the most prolific writer, as indicated by the h-index and m-index, and Liu Shirong was the most commonly co-cited author. A paper published in the International Journal of Molecular Sciences in 2017 had the highest number of citations. The keywords “expression” and “gut microbiota” appeared most frequently, and the top three groups of diseases that appeared among keywords were cancer (colorectal, et al.), inflammatory bowel disease (Crohn’s disease and ulcerative colitis), and neurological disorders (anxiety, Parkinson’s disease, et al.). This bibliometric study revealed that most studies have focused on miRNAs (e.g., miR-21, miR-155, and miR-146a), gut microbes (e.g., Escherichia coli, Bifidobacterium, and Fusobacterium nucleatum), and gut bacteria metabolites (e.g., butyric acid), which have the potential to improve the diagnosis, treatment, and prognosis of diseases. We found that therapeutic strategies targeting the miRNA–microbiome axis focus on miRNA drugs produced in vitro; however, some studies suggest that in vivo fermentation can greatly increase the stability and reduce the degradation of miRNA. Therefore, this method is worthy of further research.

Host-microbiota interactions shaping T-cell response and tolerance in type 1 diabetes

Type-1 Diabetes (T1D) is a complex polygenic autoimmune disorder involving T-cell driven beta-cell destruction leading to hyperglycemia. There is no cure for T1D and patients rely on exogenous insulin administration for disease management. T1D is associated with specific disease susceptible alleles. However, the predisposition to disease development is not solely predicted by them. This is best exemplified by the observation that a monozygotic twin has just a 35% chance of developing T1D after their twin's diagnosis. This makes a strong case for environmental triggers playing an important role in T1D incidence. Multiple studies indicate that commensal gut microbiota and environmental factors that alter their composition might exacerbate or protect against T1D onset. In this review, we discuss recent literature highlighting microbial species associated with T1D. We explore mechanistic studies which propose how some of these microbial species can modulate adaptive immune responses in T1D, with an emphasis on T-cell responses. We cover topics ranging from gut-thymus and gut-pancreas communication, microbial regulation of peripheral tolerance, to molecular mimicry of islet antigens by microbial peptides. In light of the accumulating evidence on commensal influences in neonatal thymocyte development, we also speculate on the link between molecular mimicry and thymic selection in the context of T1D pathogenesis. Finally, we explore how these observations could inform future therapeutic approaches in this disease.

Abnormal intestinal milieu in posttraumatic stress disorder is not impacted by treatment that improves symptoms

Posttraumatic stress disorder (PTSD) is a psychiatric disorder, resulting from exposure to traumatic events. Current recommended first-line interventions for the treatment of PTSD include evidence-based psychotherapies, such as cognitive processing therapy (CPT). Psychotherapies are effective for reducing PTSD symptoms, but approximately two-thirds of veterans continue to meet diagnostic criteria for PTSD after treatment, suggesting there is an incomplete understanding of what factors sustain PTSD. The intestine can influence the brain and this study evaluated intestinal readouts in subjects with PTSD. Serum samples from controls without PTSD (n = 40) from the Duke INTRuST Program were compared with serum samples from veterans with PTSD (n = 40) recruited from the Road Home Program at Rush University Medical Center. Assessments included microbial metabolites, intestinal barrier, and intestinal epithelial cell function. In addition, intestinal readouts were assessed in subjects with PTSD before and after a 3-wk CPT-based intensive treatment program (ITP) to understand if treatment impacts the intestine. Compared with controls, veterans with PTSD had a proinflammatory intestinal environment including lower levels of microbiota-derived metabolites, such as acetic, lactic, and succinic acid, intestinal barrier dysfunction [lipopolysaccharide (LPS) and LPS-binding protein], an increase in HMGB1, and a concurrent increase in the number of intestinal epithelial cell-derived extracellular vesicles. The ITP improved PTSD symptoms but no changes in intestinal outcomes were noted. This study confirms the intestine is abnormal in subjects with PTSD and suggests that effective treatment of PTSD does not alter intestinal readouts. Targeting beneficial changes in the intestine may be an approach to enhance existing PTSD treatments.NEW & NOTEWORTHY This study confirms an abnormal intestinal environment is present in subjects with PTSD. This study adds to what is already known by examining the intestinal barrier and evaluating the relationship between intestinal readouts and PTSD symptoms and is the first to report the impact of PTSD treatment (which improves symptoms) on intestinal readouts. This study suggests that targeting the intestine as an adjunct approach could improve the treatment of PTSD.

Epigenetic regulation by gut microbiota

The gastrointestinal tract is continuously exposed to trillions of commensal microbes, collectively termed the microbiota, which are environmental stimuli that can direct health and disease within the host. In addition to well-established bacterial sensing pathways, microbial signals are also integrated through epigenetic modifications that calibrate the transcriptional program of host cells without altering the underlying genetic code. Microbiota-sensitive epigenetic changes include modifications to the DNA or histones, as well as regulation of non-coding RNAs. While microbiota-sensitive epigenetic mechanisms have been described in both local intestinal cells and as well in peripheral tissues, further research is required to fully decipher the complex relationship between the host and microbiota. This Review highlights current understandings of epigenetic regulation by gut microbiota and important implications of these findings in guiding therapeutic approaches to prevent or combat diseases driven by impaired microbiota-host interactions.

Gut Dysbiosis in Pancreatic Diseases: A Causative Factor and a Novel Therapeutic Target

Pancreatic-related disorders such as pancreatitis, pancreatic cancer, and type 1 diabetes mellitus (T1DM) impose a substantial challenge to human health and wellbeing. Even though our understanding of the initiation and progression of pancreatic diseases has broadened over time, no effective therapeutics is yet available for these disorders. Mounting evidence suggests that gut dysbiosis is closely related to human health and disease, and pancreatic diseases are no exception. Now much effort is under way to explore the correlation and eventually potential causation between the gut microbiome and the course of pancreatic diseases, as well as to develop novel preventive and/or therapeutic strategies of targeted microbiome modulation by probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT) for these multifactorial disorders. Attempts to dissect the intestinal microbial landscape and its metabolic profile might enable deep insight into a holistic picture of these complex conditions. This article aims to review the subtle yet intimate nexus loop between the gut microbiome and pancreatic diseases, with a particular focus on current evidence supporting the feasibility of preventing and controlling pancreatic diseases via microbiome-based therapeutics and therapies.

Variation of Serum Uric Acid Is Associated With Gut Microbiota in Patients With Diabetes Mellitus

Diabetes mellitus is a metabolic disease closely related to a disordered gut microbiome. Diabetic patients usually suffer from various metabolic disorders, such as increased serum uric acid levels. Although serum uric acid levels depend partially on intestine excretion, the relationship between uric acid and gut microbiome in diabetic patients remains unknown. We collected a total of 126 fecal samples from diabetic patients for 16S ribosomal RNA gene amplicon sequencing and recorded clinical data. We analyzed the correlation between clinical indicators and gut microbiota of diabetic patients using Spearman analysis. Since uric acid was the most prominent one, we classified diabetic patients based on their uric acid levels to find the microbiome associated with uric acid disturbance. We constructed Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway profiles using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) to identify variations between the different groups. Among all the clinical indicators, uric acid had the strongest correlation with gut microbiota. First, we divided the patients into three groups according to their uric acid levels. The two low uric acid groups were similar, while the elevated uric acid group had significant differences in gut microbiota and metabolic pathways. The elevated uric acid group had a significantly lower gut microbiota diversity. At the genus level, this group had remarkably higher Escherichia–Shigella amounts and notably lower Faecalibacterium, Oscillospiraceae_UCG−002, and Oscillospiraceae_UCG−005 amounts. The gut microbiota of the high uric acid group was predicted to be enriched in metabolism, human diseases, and lipopolysaccharide biosynthesis. Since the two low uric acid groups were similar, we regrouped and matched the abnormal uric acid patients with normal uric acid patients. The differences in gut microbiota and metabolic pathways related to nucleotide metabolism became more significant. The serum uric acid levels were associated with gut microbiome changes. This might be related to uric acid metabolism by gut microbes. Our study indicates that targeting the gut microbiome could help manage elevated uric acid levels.

The Impact of Intestinal Microorganisms and Their Metabolites on Type 1 Diabetes Mellitus

BACKGROUND

Type 1 diabetes mellitus (T1DM) is an autoimmune disease with a complex etiology comprising numerous genetic and environmental factors; however, many of the mechanisms underlying disease development remain unclear. Nevertheless, a critical role has recently been assigned to intestinal microorganisms in T1DM disease pathogenesis. In particular, a decrease in intestinal microbial diversity, increase in intestinal permeability, and the translocation of intestinal bacteria to the pancreas have been reported in patients and animal models with T1DM. Moreover, intestinal microbial metabolites differ between healthy individuals and patients with T1DM. Specifically, short-chain fatty acid (SCFA) production, which contributes to intestinal barrier integrity and immune response regulation, is significantly reduced in patients with T1DM. Considering this correlation between intestinal microorganisms and T1DM, many studies have investigated the potential of intestinal microbiota in preventive and therapeutic strategies for T1DM.

OBJECTIVE

The aim of this review is to provide further support for the notion that intestinal microbiota contributes to the regulation of T1DM occurrence and development. In particular, this article reviews the involvement of the intestinal microbiota and the associated metabolites in T1DM pathogenesis, as well as recent studies on the involvement of the intestinal microbiota in T1DM prevention and treatment.

CONCLUSION

Intestinal microbes and their metabolites contribute to T1DM occurrence and development and may become a potential target for novel therapeutics.