Involvement of tissue bacteria in the onset of diabetes in humans: evidence for a concept

Identifying the location-dependent adipose tissue bacterial DNA signatures in obese patients that predict body weight loss

Recent sets of evidence have described profiles of 16S rDNA sequences in host tissues, notably in fat pads that are significantly overrepresented and can serve as signatures of metabolic disease. However, these recent and original observations need to be further detailed and functionally defined. Here, using state-of-the-art targeted DNA sequencing and discriminant predictive approaches, we describe, from the longitudinal FLORINASH cohort of patients who underwent bariatric surgery, visceral, and subcutaneous fat pad-specific bacterial 16SrRNA signatures. The corresponding Porphyromonadaceae, Campylobacteraceae, Prevotellaceae, Actimomycetaceae, Veillonellaceae, Anaerivoracaceae, Fusobacteriaceae, and the Clostridium family XI 16SrRNA DNA segment profiles are signatures of the subcutaneous adipose depot while Pseudomonadaceae and Micrococcacecae, 16SrRNA DNA sequence profiles characterize the visceral adipose depot. In addition, we have further identified that a specific pre-bariatric surgery adipose tissue bacterial DNA signature predicts the efficacy of body weight loss in obese patients 5-10 years after the surgery. 16SrRNA signatures discriminate (ROC ~ 1) the patients who did not maintain bodyweight loss and those who did. Second, from the 16SrRNA sequences we infer potential pathways suggestive of catabolic biochemical activities that could be signatures of subcutaneous adipose depots that predict body weight loss.

Insights into the blood, gut, and oral microbiomes in Chinese patients with myocardial infarction: a case-control study

BACKGROUND

Emerging evidence suggests that changes in the blood microbes might be associated with cardiovascular disease, especially myocardial infarction (MI). However, some researchers are questioning whether a true "blood microbiome" actually exists. They hypothesized that these microbes may translocate into the bloodstream from the gut or oral cavities. To test this hypothesis, we analyzed the microbial composition, diversity, and potential role in disease progression by comparing blood, gut, and oral microbiota profiles in a cohort of MI patients and healthy controls.

METHODS

In this study, 144 samples, including blood, fecal, and saliva, were collected from twenty-four myocardial infarction patients and twenty-four healthy controls. These samples were analyzed using 16 S rRNA sequencing to characterize the microbial profiles across the three distinct microbial compartments. Differential analyses were conducted to find key differential microbiota for MI. Spearman's rank correlation analysis was used to study the association between microbiota and clinical indicators.

RESULTS

Our findings revealed striking microbial shifts across blood, gut, and oral compartments in MI patients compared to healthy controls. In the blood, we observed significant enrichment of the phyla Armatimonadota and Caldatribacteriota, alongside the genera Bacillus, Pedobacter, and Odoribacter. The gut microbiota of MI patients showed a notable increase in the phyla Proteobacteria, Verrucomicrobiota, Cyanobacteria, Synergistota, and Crenarchaeota, as well as the genera Eubacterium_coprostanoligenes_group, Rothia, Akkermansia, Lachnospiraceae_ NK4A136_ group, and Eubacterium_ruminantium_group. Meanwhile, the oral microbiota of MI patients was uniquely enriched with the phylum Elusimicrobiota and the genera Streptococcus, Rothia, and Granulicatella. These distinct microbial signatures highlight compartment-specific alterations that may play a role in the pathophysiology of MI. Additionally, LEfSe analysis identified 64 distinct taxa that differed across the three compartments. Of these, eight taxa were unique to blood, eighteen to the gut, and thirty-eight to the oral microbiota, all of which demonstrated significant associations with clinical markers of MI. Functional pathways were predicted and analyzed via KEGG annotation, but no statistically significant differences were found between MI patients and healthy controls in any of the microbiome compartments.

CONCLUSION

This study demonstrates significant alterations in the blood, gut, and oral microbiome profiles of MI patients, identifying specific bacterial taxa strongly associated with key markers of myocardial infarction. The unique microbial patterns detected in the blood provide compelling evidence for the existence of a stable core blood microbiome, highlighting its importance as a key contributor to cardiovascular health and disease progression.

Distinct blood and oral microbiome profiles reveal altered microbial composition and functional pathways in myocardial infarction patients

Introduction

The blood microbiome, increasingly recognized as a distinct microbial niche, may originate partly from oral translocation. We systematically compared circulating and oral microbiome profiles between healthy individuals and myocardial infarction (MI) patients to identify disease-associated signatures.

Methods

The current study recruited 20 participants, including 10 healthy controls and 10 patients with MI. Blood and Saliva samples were collected from each participant to analyze the association between blood and oral microbiome in MI patients using 16S rRNA gene sequencing.

Results

The blood microbiome showed significantly greater alpha diversity than the oral microbiome (p<0.05), but beta diversity did not differ significantly. The blood microbiome in MI patients had higher levels of Firmicutes, Bacteroidota, Actinobacteriota, genus Bacteroides, and lower Proteobacteria, whereas the oral microbiome was dominated by Firmicutes, Bacteroidota, Veillonella, and Prevotella_7. LEfSe analysis revealed distinct blood microbial taxa-Actinobacteria in MI patients and Enterobacterales in controls. In contrast, the oral microbiota of healthy subjects was enriched in Rothia, Micrococcaceae, and Micrococcales, while no distinct taxa were associated with MI. Both blood and oral microbiomes showed significant functional pathway differences (KEGG) between groups. Additionally, microbiome signatures significantly correlated with clinical and demographic markers.

Discussion

Our study demonstrates that the blood harbors a distinct microbiome characterized by specific microbial taxa and functional pathways rather than merely reflecting oral bacterial translocation. These findings suggest that the circulating microbiome may play an active role in the pathology of MI. Furthermore, we identified significant associations between these microbial signatures and clinical disease markers. This highlights the potential importance of the blood microbiome in understanding the mechanisms underlying MI and its diagnostic or therapeutic implications.

Unveiling the interplay among skin microbiota, cytokines, and T2DM: an insightful Mendelian randomization study

BACKGROUND

Previous observational studies have indicated a correlation between the skin microbiome and Type 2 diabetes (T2DM). It is hypothesized that this causal relationship may be influenced by inflammatory responses. However, these factors as determinants of T2DM remain largely unexplored.

METHOD

This study incorporated data from the GWAS database on the skin microbiome, 91 types of inflammatory cytokines, and T2DM. We employed two-sample MR and multivariable MR methods to assess the correlation between the skin microbiome and T2DM, and to investigate whether this correlation is affected by inflammatory cytokines.

RESULTS

The results of the two-sample MR analysis indicate that within the skin microbiome, genetically predicted genus: Acinetobacter, class: Alphaproteobacteria, genus: Bacteroides, ASV005[Propionibacterium granulosum], and ASV072[Rothia mucilaginosa] are associated with an increased risk of T2DM, while phylum: Proteobacteria, genus: Enhydrobacter, family: Clostridiales, ASV006[Staphylococcus hominis] serve as protective factors against T2DM. Among the inflammatory cytokines, levels of Macrophage colony-stimulating factor 1, Tumor necrosis factor receptor superfamily member 9, Urokinase-type plasminogen activator, and C-C motif chemokine 28 are associated with an increased risk of T2DM. Multivariable MR analysis further revealed that Macrophage colony-stimulating factor 1 levels act as a mediating factor between ASV072[Rothia mucilaginosa] and T2DM.

CONCLUSION

In this study, we found a connection between the skin microbiome and T2DM, with inflammatory cytokines playing a key role in this relationship. This research helps us better understand this complex link and shows that addressing inflammation is important for preventing and treating diabetes. This could greatly benefit public health by reducing the impact of diabetes and its complications. Our results suggest that future studies should explore the specific biological interactions between the skin microbiome and diabetes to develop more effective risk management and treatment strategies from a microbial perspective.

The Microbiome and Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a condition wherein excessive fat accumulates in the liver, leading to inflammation and potential liver damage. In this narrative review, we evaluate the tissue microbiota, how they arise and their constituent microbes, and the role of the intestinal and hepatic microbiota in MASLD. The history of bacteriophages (phages) and their occurrence in the microbiota, their part in the potential causation of MASLD, and conversely, "phage therapy" for antibiotic resistance, obesity, and MASLD, are all described. The microbiota metabolism of bile acids and dietary tryptophan and histidine is defined, together with the impacts of their individual metabolites on MASLD pathogenesis. Both periodontitis and intestinal microbiota dysbiosis may cause MASLD, and how individual microorganisms and their metabolites are involved in these processes is discussed. Novel treatment opportunities for MASLD involving the microbiota exist and include fecal microbiota transplantation, probiotics, prebiotics, synbiotics, tryptophan dietary supplements, intermittent fasting, and phages or their holins and endolysins. Although FDA is yet to approve phage therapy in clinical use, there are multiple FDA-approved clinical trials, and this may represent a new horizon for the future treatment of MASLD.

The dual role of gut microbiota in pancreatic cancer: new insights into onset and treatment

Pancreatic cancer ranks among the most lethal digestive malignancies, exhibiting a steadily increasing incidence and mortality worldwide. Despite significant advances in cancer research, the 5-year survival rate remains below 10%, predominantly due to delayed diagnosis and limited therapeutic options. Concurrently, the gut microbiota-an integral component of host physiology-has emerged as a crucial player in the pathogenesis of pancreatic cancer. Mounting evidence indicates that alterations in gut microbial composition and function may influence tumor initiation, progression, and response to therapy. This review provides an in-depth examination of the intricate interplay between the gut microbiome and pancreatic cancer, highlighting potential diagnostic biomarkers and exploring microbiome-targeted therapeutic strategies to improve patient outcomes.

Hawthorn leaf and its extract alleviate high-fat diet-induced obesity and modulate gut microbiome in mice

Obesity has emerged as a global health issue with its prevalence continuously increasing and being associated with multiple comorbidities. Although existing medications are effective, they often come with significant side effects, making dietary therapy an advantageous alternative. Hawthorn leaves and their active component, vitexin, have shown potential in regulating lipid metabolism and improving gut microbiota imbalance. This study utilized a high-fat diet-induced obese mouse model, administering different doses of hawthorn leaves and vitexin for 13 weeks, and employed 16S rRNA sequencing and metabolomics to analyze the composition of gut microbiota and metabolites. The results demonstrated that hawthorn leaves and vitexin significantly slowed body weight gain, improved glucose tolerance, regulated blood lipid levels, and downregulated the expression of obesity-related gene in mice (ppar-α, ppar-γ, fas). Additionally, the treatment groups showed a significant improvement in gut microbiota diversity. Both vitexin and hawthorn leaves increased the abundance of Kineothrix, Paramuribaculum, Lawsonibacter (which belong to the Bacillota phylum) and Olsenella (Actinobacteria phylum), while reducing the abundance of Anaerotignum (Bacillota phylum). Moreover, the hawthorn leaves and vitexin treatments may alleviate obesity-related symptoms by increasing the fecal content of testosterone propionate, formoterol, and isoleucyl-prolyl-proline, and decreasing the content of Trolox. These findings highlight the potential of hawthorn leaves and vitexin as functional foods for obesity management by modulating gut microbiota pathways, offering a promising dietary therapy approach.

Human reference microbiome profiles of different body habitats in healthy individuals

Introduction

This study aimed to establish the human reference microbiome profiles in blood, saliva, and stool of healthy individuals, serving as reference values to identify microbiome alterations in human disease.

Methods

The study population consisted of a reference group of healthy adults and a second group consisting of adults with periodontal disease (PD). Blood, saliva, and stool samples were subjected to 16S rRNA sequencing. Reference intervals of alpha diversity indices were calculated. To reduce the effects of inherent limitations of microbiome data, the taxonomic profiles of the reference group were estimated as log-scaled fold change (logFC) in the abundance of microorganisms between two habitats within the subjects.

Results

For stool and saliva microbiomes, differences in the abundances of Firmicutes, Patescibacteria, and Verrucomicrobia distinguished healthy from PD subjects (95% confidence interval (CI) of logFC: [-0.18, 0.31], [-1.19, -0.34], and [-3.68, -2.90], respectively). Differences in the abundances of Cyanobacteria, Fusobacteria, and Tenericutes in stool and blood microbiome of healthy subjects fell within 95% CI of logFC [-0.38, 0.61], [-4.14, -3.01], and [1.66, 2.77], respectively. In saliva and blood, differences in the abundances of Epsilonbacteraeota, Firmicutes, Fusobacteria, and Proteobacteria could be used as reference values (95% CI of logFC: [-3.67, -2.47], [-0.35, 0.49], [-4.59, -3.26], and [-1.20, 0.07], respectively).

Discussion

As the reference microbiome profiles could discern healthy subjects and individuals with PD, a relatively mild disease state, they can be applied as reference values representing the healthy status of the microbiome and for screening of disease states, preferably in preclinical stages.

The profile of blood microbiome in new-onset type 1 diabetes children

Blood microbiome signatures in patients with type 1 diabetes (T1D) remain unclear. We profile blood microbiome using 16S rRNA gene sequencing in 77 controls and 64 children with new-onset T1D, and compared it with the gut and oral microbiomes. The blood microbiome of patients with T1D is characterized by increased diversity and perturbed microbial features, with a significant increase in potentially pathogenic bacteria compared with controls. Thirty-six representative genera of blood microbiome were identified by random forest analysis, providing strong discriminatory power for T1D with an AUC of 0.82. PICRUSt analysis suggested that bacteria capable of inducing inflammation were more likely to enter the bloodstream in T1D. The overlap of the gut and oral microbiome with the blood microbiome implied potential translocation of bacteria from the gut and oral cavity to the bloodstream. Our study raised the necessity of further mechanistic investigations into the roles of blood microbiome in T1D.

Blood Microbiota and Its Products: Mechanisms of Interference with Host Cells and Clinical Outcomes

In healthy conditions, blood was considered a sterile environment until the development of new analytical approaches that allowed for the detection of circulating bacterial ribosomal DNA. Currently, debate exists on the origin of the blood microbiota. According to advanced research using dark field microscopy, fluorescent in situ hybridization, flow cytometry, and electron microscopy, so-called microbiota have been detected in the blood. Conversely, others have reported no evidence of a common blood microbiota. Then, it was hypothesized that blood microbiota may derive from distant sites, e.g., the gut or external contamination of blood samples. Alteration of the blood microbiota's equilibrium may lead to dysbiosis and, in certain cases, disease. Cardiovascular, respiratory, hepatic, kidney, neoplastic, and immune diseases have been associated with the presence of Gram-positive and Gram-negative bacteria and/or their products in the blood. For instance, lipopolysaccharides (LPSs) and endotoxins may contribute to tissue damage, fueling chronic inflammation. Blood bacteria can interact with immune cells, especially with monocytes that engulf microorganisms and T lymphocytes via spontaneous binding to their membranes. Moreover, LPSs, extracellular vesicles, and outer membrane vesicles interact with red blood cells and immune cells, reaching distant organs. This review aims to describe the composition of blood microbiota in healthy individuals and those with disease conditions. Furthermore, special emphasis is placed on the interaction of blood microbiota with host cells to better understand disease mechanisms.

Tissue-resident bacteria in metabolic diseases: emerging evidence and challenges

Although the impact of the gut microbiome on health and disease is well established, there is controversy regarding the presence of microorganisms such as bacteria and their products in organs and tissues. However, recent contamination-aware findings of tissue-resident microbial signatures provide accumulating evidence in support of bacterial translocation in cardiometabolic disease. The latter provides a distinct paradigm for the link between microbial colonizers of mucosal surfaces and host metabolism. In this Perspective, we re-evaluate the concept of tissue-resident bacteria including their role in metabolic low-grade tissue and systemic inflammation. We examine the limitations and challenges associated with studying low bacterial biomass samples and propose experimental and analytical strategies to overcome these issues. Our Perspective aims to encourage further investigation of the mechanisms linking tissue-resident bacteria to host metabolism and their potentially actionable health implications for prevention and treatment.

Distinct compositions and functions of circulating microbial DNA in the peripheral blood compared to fecal microbial DNA in healthy individuals

The crucial function of circulating microbial DNA (cmDNA) in peripheral blood is gaining recognition because of its importance in normal physiology and immunity in healthy individuals. Evidence suggests that cmDNA in peripheral blood is derived from highly abundant, translocating gut microbes. However, the associations with and differences between cmDNA in peripheral blood and the gut microbiome remain unclear. We collected blood, urine, and fecal samples from volunteers to compare their microbial information via 16S rDNA sequencing. The results revealed that, compared with gut microbial DNA, cmDNA in peripheral blood was associated with reduced diversity and a distinct microbiota composition. The cmDNA in the blood reflects the biochemical processes of microorganisms, including synthesis, energy conversion, degradation, and adaptability, surpassing that of fecal samples. Interestingly, cmDNA in blood showed a limited presence of DNA from anaerobes and gram-positive bacteria, which contrast with the trend observed in fecal samples. Furthermore, analysis of cmDNA revealed traits associated with mobile elements and potential pathologies, among others, which were minimal in stool samples. Notably, cmDNA analysis indicated similarities between the microbial functions and phenotypes in blood and urine samples, although greater diversity was observed in urine samples. Source Tracker analysis suggests that gut microbes might not be the main source of blood cmDNA, or a selective mechanism allows only certain microbial DNA into the bloodstream. In conclusion, our study highlights the composition and potential functions associated with cmDNA in peripheral blood, emphasizing its selective presence; however, further research is required to elucidate the mechanisms involved.IMPORTANCEOur research provides novel insights into the unique characteristics and potential functional implications of circulating microbial DNA (cmDNA) in peripheral blood. Unlike other studies that analyzed sequencing data from fecal or blood microbiota in different study cohorts, our comparative analysis of cmDNA from blood, urine, and fecal samples from the same group of volunteers revealed a distinct blood-specific cmDNA composition. We discovered a decreased diversity of microbial DNA in blood samples compared to fecal samples as well as an increased presence of biochemical processes microbial DNA in blood. Notably, we add to the existing knowledge by documenting a reduced abundance of anaerobes and gram-positive bacteria in blood compared to fecal samples according to the analysis of cmDNA and gut microbial DNA, respectively. This observation suggested that a potential selective barrier or screening mechanism might filter microbial DNA molecules, indicating potential selectivity in the translocation process which contrasts with the traditional view that cmDNA primarily originates from random translocation from the gut and other regions. By highlighting these differences, our findings prompt a reconsideration of the origin and role of cmDNA in blood circulation and suggest that selective processes involving more complex biological mechanisms may be involved.

Gut microbiota in overweight and obesity: crosstalk with adipose tissue

Overweight and obesity are characterized by excessive fat mass accumulation produced when energy intake exceeds energy expenditure. One plausible way to control energy expenditure is to modulate thermogenic pathways in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Among the different environmental factors capable of influencing host metabolism and energy balance, the gut microbiota is now considered a key player. Following pioneering studies showing that mice lacking gut microbes (that is, germ-free mice) or depleted of their gut microbiota (that is, using antibiotics) developed less adipose tissue, numerous studies have investigated the complex interactions existing between gut bacteria, some of their membrane components (that is, lipopolysaccharides), and their metabolites (that is, short-chain fatty acids, endocannabinoids, bile acids, aryl hydrocarbon receptor ligands and tryptophan derivatives) as well as their contribution to the browning and/or beiging of WAT and changes in BAT activity. In this Review, we discuss the general physiology of both WAT and BAT. Subsequently, we introduce how gut bacteria and different microbiota-derived metabolites, their receptors and signalling pathways can regulate the development of adipose tissue and its metabolic capacities. Finally, we describe the key challenges in moving from bench to bedside by presenting specific key examples.

Fenofibrate reduces glucose-induced barrier dysfunction in feline enteroids

Diabetes mellitus (DM) is a common chronic metabolic disease in humans and household cats that is characterized by persistent hyperglycemia. DM is associated with dysfunction of the intestinal barrier. This barrier is comprised of an epithelial monolayer that contains a network of tight junctions that adjoin cells and regulate paracellular movement of water and solutes. The mechanisms driving DM-associated barrier dysfunction are multifaceted, and the direct effects of hyperglycemia on the epithelium are poorly understood. Preliminary data suggest that fenofibrate, An FDA-approved peroxisome proliferator-activated receptor-alpha (PPARα) agonist drug attenuates intestinal barrier dysfunction in dogs with experimentally-induced DM. We investigated the effects of hyperglycemia-like conditions and fenofibrate treatment on epithelial barrier function using feline intestinal organoids. We hypothesized that glucose treatment directly increases barrier permeability and alters tight junction morphology, and that fenofibrate administration can ameliorate these deleterious effects. We show that hyperglycemia-like conditions directly increase intestinal epithelial permeability, which is mitigated by fenofibrate. Moreover, increased permeability is caused by disruption of tight junctions, as evident by increased junctional tortuosity. Finally, we found that increased junctional tortuosity and barrier permeability in hyperglycemic conditions were associated with increased protein kinase C-α (PKCα) activity, and that fenofibrate treatment restored PKCα activity to baseline levels. We conclude that hyperglycemia directly induces barrier dysfunction by disrupting tight junction structure, a process that is mitigated by fenofibrate. We further propose that counteracting modulation of PKCα activation by increased intracellular glucose levels and fenofibrate is a key candidate regulatory pathway of tight junction structure and epithelial permeability.

Abnormal blood microbiota profiles are associated with inflammation and immune restoration in HIV/AIDS individuals

The characteristics of blood microbiota in HIV-infected individuals and their relevance to disease progression are still unknown, despite alterations in gut microbiota diversity and composition in HIV-infected individuals. Here, we present evidence of increased blood microbiota diversity in HIV-infected individuals, which may result from gut microbiota translocation. Also, we identify a group of microbes, Porphyromonas gingivalis, Prevotella sp. CAG:5226, Eubacterium sp. CAG:251, Phascolarctobacterium succinatutens, Anaerobutyricum hallii, Prevotella sp. AM34-19LB, and Phocaeicola plebeius, which are linked to poor immunological recovery. This work provides a scientific foundation toward therapeutic strategies targeting blood microbiota for immune recovery of HIV infection.

The visceral adipose tissue bacterial microbiota provides a signature of obesity based on inferred metagenomic functions

BACKGROUND

Metabolic inflammation mediated obesity requires bacterial molecules to trigger immune and adipose cells leading to inflammation and adipose depot development. In addition to the well-established gut microbiota dysbiosis, a leaky gut has been identified in patients with obesity and animal models, characterized by the presence of a tissue microbiota in the adipose fat pads.

METHODS

To determine its potential role, we sequenced the bacterial 16 S rRNA genes in the visceral adipose depot of patients with obesity. Taking great care (surgical, biochemical, and bioinformatic) to avoid environmental contaminants. We performed statistical discriminant analyses to identify specific signatures and constructed network of interactions between variables.

RESULTS

The data showed that a specific 16SrRNA gene signature was composed of numerous bacterial families discriminating between lean versus patients with obesity and people with severe obesity. The main discriminant families were Burkholderiaceae, Yearsiniaceae, and Xanthomonadaceae, all of which were gram-negative. Interestingly, the Morganellaceae were totally absent from people without obesity while preponderant in all in patients with obesity. To generate hypotheses regarding their potential role, we inferred metabolic pathways from the 16SrRNA gene signatures. We identified several pathways associated with adenosyl-cobalamine previously described to be linked with adipose tissue development. We further identified chorismate biosynthesis, which is involved in aromatic amino-acid metabolism and could play a role in fat pad development. This innovative approach generates novel hypotheses regarding the gut to adipose tissue axis.

CONCLUSIONS

This innovative approach generates novel hypotheses regarding the gut to adipose tissue axis in obesity and notably the potential role of tissue microbiota.

Platelets bridging the gap between gut dysbiosis and neuroinflammation in stress-linked disorders: A narrative review

In this narrative review, we examine the association between gut dysbiosis, neuroinflammation, and stress-linked disorders, including depression, anxiety, and post-traumatic stress disorder (PTSD), and investigate whether tryptophan (TRP) metabolism and platelets play a role in this association. The mechanisms underlying the aetiology of stress-linked disorders are complex and not yet completely understood. However, a potential link between chronic inflammation and these disorders may potentially be found in TRP metabolism and platelets. By critically analysing existing literature on platelets, the gut microbiome, and stress-linked disorders, we hope to elicit the role of platelets in mediating the effects on serotonin (5-HT) levels and neuroinflammation. We have included studies specifically investigating platelets and TRP metabolism in relation to inflammation, neuroinflammation and neuropsychiatric disorders. Alteration in microbial composition due to stress could contribute to increased intestinal permeability, facilitating the translocation of microbial products, and triggering the release of pro-inflammatory cytokines. This causes platelets to become hyperactive and secrete 5-HT into the plasma. Increased levels of pro-inflammatory cytokines may also lead to increased permeability of the blood-brain barrier (BBB), allowing inflammatory mediators entry into the brain, affecting the balance of TRP metabolism products, such as 5-HT, kynurenic acid (KYNA), and quinolinic acid (QUIN). These alterations may contribute to neuroinflammation and possible neurological damage. Furthermore, platelets can cross the compromised BBB and interact with astrocytes and neurons, leading to the secretion of 5-HT and pro-inflammatory factors, exacerbating inflammatory conditions in the brain. The mechanisms underlying neuroinflammation resulting from peripheral inflammation are still unclear, but the connection between the brain and gut through the bloodstream could be significant. Identifying peripheral biomarkers and mechanisms in the plasma that reflect neuroinflammation may be important. This review serves as a foundation for further research on the association between the gut microbiome, blood microbiome, and neuropsychiatric disorders. The integration of these findings with protein and metabolite markers in the blood may expand our understanding of the subject.

Intestinal permeability and peripheral immune cell composition are altered by pregnancy and adiposity at mid- and late-gestation in the mouse

It is clear that the gastrointestinal tract influences metabolism and immune function. Most studies to date have used male test subjects, with a focus on effects of obesity and dietary challenges. Despite significant physiological maternal adaptations that occur across gestation, relatively few studies have examined pregnancy-related gut function. Moreover, it remains unknown how pregnancy and diet can interact to alter intestinal barrier function. In this study, we investigated the impacts of pregnancy and adiposity on maternal intestinal epithelium morphology, in vivo intestinal permeability, and peripheral blood immunophenotype, using control (CTL) and high-fat (HF) fed non-pregnant female mice and pregnant mice at mid- (embryonic day (E)14.5) and late (E18.5) gestation. We found that small intestine length increased between non-pregnant mice and dams at late-gestation, but ileum villus length, and ileum and colon crypt depths and goblet cell numbers remained similar. Compared to CTL-fed mice, HF-fed mice had reduced small intestine length, ileum crypt depth and villus length. Goblet cell numbers were only consistently reduced in HF-fed non-pregnant mice. Pregnancy increased in vivo gut permeability, with a greater effect at mid- versus late-gestation. Non-pregnant HF-fed mice had greater gut permeability, and permeability was also increased in HF-fed pregnant dams at mid but not late-gestation. The impaired maternal gut barrier in HF-fed dams at mid-gestation coincided with changes in maternal blood and bone marrow immune cell composition, including an expansion of circulating inflammatory Ly6Chigh monocytes. In summary, pregnancy has temporal effects on maternal intestinal structure and barrier function, and on peripheral immunophenotype, which are further modified by HF diet-induced maternal adiposity. Maternal adaptations in pregnancy are thus vulnerable to excess maternal adiposity, which may both affect maternal and child health.

Are gut dysbiosis, barrier disruption, and endotoxemia related to adipose tissue dysfunction in metabolic disorders? Overview of the mechanisms involved

Recently, compelling evidence points to dysbiosis and disruption of the epithelial intestinal barrier as major players in the pathophysiology of metabolic disorders, such as obesity. Upon the intestinal barrier disruption, components from bacterial metabolism and bacteria itself can reach peripheral tissues through circulation. This has been associated with the low-grade inflammation that characterizes obesity and other metabolic diseases. While circulating bacterial DNA has been postulated as a common feature of obesity and even type 2 diabetes, almost no focus has been given to the existence and effects of bacteria in peripheral tissues, namely the adipose tissue. As a symbiont population, it is expected that gut microbiota modulate the immunometabolism of the host, thus influencing energy balance mechanisms and inflammation. Gut inflammatory signals cause direct deleterious inflammatory responses in adipose tissue and may also affect key gut neuroendocrine mechanisms governing nutrient sensing and energy balance, like incretins and ghrelin, which play a role in the gut-brain-adipose tissue axis. Thus, it is of major importance to disclose how gut microbiota and derived signals modulate neuroendocrine and inflammatory pathways, which contribute to the dysfunction of adipose tissue and to the metabolic sequelae of obesity and related disorders. This review summarizes the current knowledge regarding these topics and identifies new perspectives in this field of research, highlighting new pathways toward the reduction of the inflammatory burden of metabolic diseases.

A bacterial signature-based method for the identification of seven forensically relevant human body fluids

Detection and identification of body fluids plays a crucial role in criminal investigation, as it provides information on the source of the DNA as well as corroborative evidence regarding the crime committed, scene, and/or association with persons of interest. Historically, forensic serological methods have been chemical, immunological, catalytic, spectroscopic, and/or microscopic in nature. However, most of these methods are presumptive, with few robust confirmatory exceptions. In recent years several new molecular methods (mRNA, miRNA, DNA methylation, etc.) have been proposed; although promising, these methods require high quality human DNA or RNA. Additional steps are required in RNA based methods. Additionally, RNA based methods cannot be used for old cases where only DNA extracts remain to sample from. In this study, a novel non-human DNA (microbiome) based method was developed for the identification of the majority of forensically relevant human biological samples. Eight hundred and twelve (n = 812) biological samples (semen, vaginal fluid, menstrual blood, saliva, feces, urine, and blood) were collected and preserved using methods commonly used in forensic laboratories for evidence collection. Variable region four (V4) of 16 S ribosomal DNA (16 S rDNA) was amplified using a dual-indexing strategy and then sequenced on the MiSeq FGx sequencing platform using the MiSeq Reagent Kit v2 (500 cycles) and following the manufacturer's protocol. Machine learning prediction models were used to assess the classification accuracy of the newly developed method. As there was no significant difference in bacterial communities between vaginal fluid, menstrual blood, and female urine, these were combined as female intimate samples. Except in urine, the bacterial structures associated with male and female body fluid samples were not significantly different from one another. The newly developed method accurately identified human body fluid samples with an overall accuracy of more than 88%. This newly developed bacterial signature-based method is fast (no additional steps are needed as the same DNA can be used for both body fluid identification and STR typing), efficient (consume less sample as a single test can identify all major body fluids), sensitive (needs only 5 pg of bacterial DNA), accurate, and can be easily added into a forensic high throughput sequencing (HTS) panel.

The Diagnostic Potential of the Human Blood Microbiome: Are We Dreaming or Awake?

Human blood has historically been considered a sterile environment. Recently, a thriving microbiome dominated by Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes phyla was detected in healthy blood. The localization of these microbes is restricted to some blood cell populations, particularly the peripheral blood mononuclear cells and erythrocytes. It was hypothesized that the blood microbiome originates from the skin-oral-gut axis. In addition, many studies have evaluated the potential of blood microbiome dysbiosis as a prognostic marker in cardiovascular diseases, cirrhosis, severe liver fibrosis, severe acute pancreatitis, type 2 diabetes, and chronic kidney diseases. The present review aims to summarize current findings and most recent evidence in the field.

Bacterial Extracellular Vesicle Composition in Human Urine and the 10-Year Risk of Abdominal Obesity

Objective: We aimed to evaluate a causal relationship between commensal bacteria and abdominal obesity. Methods: A prospective study, including 2222 adults who provided urine samples at baseline, was performed. These samples were used for assays of genomic DNA from bacterial extracellular vesicles (EVs). During the 10-year period, the incidence rates of obesity (measured as body mass index) and abdominal obesity (measured as waist circumference) were ascertained as outcomes. To evaluate associations of bacterial composition at the phylum and genus levels with the outcomes, the hazard ratio (HR) and its confidence interval (95% CI) were estimated. Results: No significant association was observed for the risk of obesity, whereas the risk of abdominal obesity was inversely associated with the composition of Proteobacteria and positively associated with that of Firmicutes (adjusted P value <0.05). In joint analysis for the combination groups of Proteobacteria and Firmicutes composition tertiles, the group with top tertiles of both Proteobacteria and Firmicutes showed a significant HR of 2.59 (95% CI: 1.33 - 5.01) compared with the reference with lower tertiles (adjusted P value <0.05). Some genera of these phyla were associated with the risk of abdominal obesity. Conclusions: These findings suggest that bacterial composition in urinary EV samples can predict the 10-year risk of abdominal obesity.

Association of Antibodies to Prevotella copri in Anti-Cyclic Citrullinated Peptide-Positive Individuals At Risk of Developing Rheumatoid Arthritis and in Patients With Early or Established Rheumatoid Arthritis

OBJECTIVE

Prevotella copri (P copri), a gut commensal, has been reported to be an immune-relevant organism in individuals with rheumatoid arthritis (RA). This study sought to evaluate anti-P copri (anti-Pc) antibody responses in our participant cohorts and to determine when in the natural history of RA such responses develop.

METHODS

We analyzed serum levels of immunoglobulin A (IgA) and IgG antibodies from a 27-kd protein of P copri (anti-Pc-p27), an immunogenic P copri protein, in study participants at risk of developing RA, participants who transitioned to RA, participants with early RA (<1 year of disease), and participants with established RA, with comparisons made to their matched controls. We also evaluated anti-Pc-p27 antibody levels in individuals stratified by RA-related autoantibody status.

RESULTS

Overall, participants with RA had significantly higher IgA anti-Pc-p27 antibody levels and trended toward higher IgG anti-Pc-p27 antibody levels compared with matched controls. When stratified by early versus established RA, participants with early RA had median IgG anti-Pc-p27 antibody levels that were overall higher, whereas median IgA anti-Pc-p27 antibody levels were statistically significantly higher in participants with established RA compared with their matched controls. In the autoantibody-specific analyses, the at-risk population with anti-cyclic citrullinated peptide (anti-CCP) antibodies, but not rheumatoid factor (RF), trended toward increased levels of IgG anti-Pc-p27. Additionally, RA participants who were seropositive for both CCP and RF had significantly increased levels of IgA anti-Pc-p27 antibodies and trended toward higher levels of IgG anti-Pc-p27 antibodies compared with matched controls.

CONCLUSION

Our findings support a potential etiologic role for P copri in both RA preclinical evolution and the subsequent pathogenesis of synovitis.

Blood Stream Microbiota Dysbiosis Establishing New Research Standards in Cardio-Metabolic Diseases, A Meta-Analysis Study

AIMS

Scientists have recently discovered a link between the circulating microbiome and homeostasis, as well as the pathogenesis of a number of metabolic diseases. It has been demonstrated that low-grade chronic inflammation is one of the primary mechanisms that has long been implicated in the risk of cardio-metabolic disease (CMDs) and its progression. Currently, the dysbiosis of circulating bacteria is considered as a key regulator for chronic inflammation in CMDs, which is why we have conducted this systemic review focused on circulating bacterial dysbiosis.

METHODS

A systemic review of clinical and research-based studies was conducted via PubMed, Scopus, Medline, and Web of Science. Literature was considered for risk of bias and patterns of intervention effects. A randomized effect model was used to evaluate the dysbiosis of circulating microbiota and clinical outcomes. We conducted a meta-analysis considering the circulating bacteria in both healthy people and people with cardio-metabolic disorders, in reports published mainly from 2008 to 2022, according to the PRISMA guidelines.

RESULTS

We searched 627 studies and, after completing the risk of bias and selection, 31 studies comprising of 11,132 human samples were considered. This meta-analysis found that dysbiosis of phyla Proteobacteria, Firmicutes, and Bacteroidetes was associated with metabolic diseases.

CONCLUSIONS

In most instances, metabolic diseases are linked to higher diversity and elevated bacterial DNA levels. Bacteroides abundance was higher in healthy people than with metabolic disorders. However, more rigorous studies are required to determine the role of bacterial dysbiosis in cardio-metabolic diseases. Understanding the relationship between dysbiosis and cardio-metabolic diseases, we can use the bacteria as therapeutics for the reversal of dysbiosis and targets for therapeutics use in cardio-metabolic diseases. In the future, circulating bacterial signatures can be used as biomarkers for the early detection of metabolic diseases.

The Blood Microbiome and Health: Current Evidence, Controversies, and Challenges

Blood is conventionally thought to be sterile. However, emerging evidence on the blood microbiome has started to challenge this notion. Recent reports have revealed the presence of genetic materials of microbes or pathogens in the blood circulation, leading to the conceptualization of a blood microbiome that is vital for physical wellbeing. Dysbiosis of the blood microbial profile has been implicated in a wide range of health conditions. Our review aims to consolidate recent findings about the blood microbiome in human health and to highlight the existing controversies, prospects, and challenges around this topic. Current evidence does not seem to support the presence of a core healthy blood microbiome. Common microbial taxa have been identified in some diseases, for instance, Legionella and Devosia in kidney impairment, Bacteroides in cirrhosis, Escherichia/Shigella and Staphylococcus in inflammatory diseases, and Janthinobacterium in mood disorders. While the presence of culturable blood microbes remains debatable, their genetic materials in the blood could potentially be exploited to improve precision medicine for cancers, pregnancy-related complications, and asthma by augmenting patient stratification. Key controversies in blood microbiome research are the susceptibility of low-biomass samples to exogenous contamination and undetermined microbial viability from NGS-based microbial profiling, however, ongoing initiatives are attempting to mitigate these issues. We also envisage future blood microbiome research to adopt more robust and standardized approaches, to delve into the origins of these multibiome genetic materials and to focus on host-microbe interactions through the elaboration of causative and mechanistic relationships with the aid of more accurate and powerful analytical tools.

New insights into the mechanisms of high-fat diet mediated gut microbiota in chronic diseases

High-fat diet (HFD) has been recognized as a primary factor in the risk of chronic disease. Obesity, diabetes, gastrointestinal diseases, neurodegenerative diseases, and cardiovascular diseases have long been known as chronic diseases with high worldwide incidence. In this review, the influences of gut microbiota and their corresponding bacterial metabolites on the mechanisms of HFD-induced chronic diseases are systematically summarized. Gut microbiota imbalance is also known to increase susceptibility to diseases. Several studies have proven that HFD has a negative impact on gut microbiota, also exacerbating the course of many chronic diseases through increased populations of Erysipelotrichaceae, facultative anaerobic bacteria, and opportunistic pathogens. Since bile acids, lipopolysaccharide, short-chain fatty acids, and trimethylamine N-oxide have long been known as common features of bacterial metabolites, we will explore the possibility of synergistic mechanisms among those metabolites and gut microbiota in the context of HFD-induced chronic diseases. Recent literature concerning the mechanistic actions of HFD-mediated gut microbiota have been collected from PubMed, Google Scholar, and Scopus. The aim of this review is to provide new insights into those mechanisms and to point out the potential biomarkers of HFD-mediated gut microbiota.

Human liver microbiota modeling strategy at the early onset of fibrosis

BACKGROUND

Gut microbiota is involved in the development of liver diseases such as fibrosis. We and others identified that selected sets of gut bacterial DNA and bacteria translocate to tissues, notably the liver, to establish a non-infectious tissue microbiota composed of microbial DNA and a low frequency live bacteria. However, the precise set of bacterial DNA, and thereby the corresponding taxa associated with the early stages of fibrosis need to be identified. Furthermore, to overcome the impact of different group size and patient origins we adapted innovative statistical approaches. Liver samples with low liver fibrosis scores (F0, F1, F2), to study the early stages of the disease, were collected from Romania(n = 36), Austria(n = 10), Italy(n = 19), and Spain(n = 17). The 16S rRNA gene was sequenced. We considered the frequency, sparsity, unbalanced sample size between cohorts to identify taxonomic profiles and statistical differences.

RESULTS

Multivariate analyses, including adapted spectral clustering with L1-penalty fair-discriminant strategies, and predicted metagenomics were used to identify that 50% of liver taxa associated with the early stage fibrosis were Enterobacteriaceae, Pseudomonadaceae, Xanthobacteriaceae and Burkholderiaceae. The Flavobacteriaceae and Xanthobacteriaceae discriminated between F0 and F1. Predicted metagenomics analysis identified that the preQ0 biosynthesis and the potential pathways involving glucoryranose and glycogen degradation were negatively associated with liver fibrosis F1-F2 vs F0.

CONCLUSIONS

Without demonstrating causality, our results suggest first a role of bacterial translocation to the liver in the progression of fibrosis, notably at the earliest stages. Second, our statistical approach can identify microbial signatures and overcome issues regarding sample size differences, the impact of environment, and sets of analyses.

TRIAL REGISTRATION

TirguMECCH ROLIVER Prospective Cohort for the Identification of Liver Microbiota, registration 4065/2014. Registered 01 01 2014.

Vitamin D, Gut Microbiota, and Cardiometabolic Diseases-A Possible Three-Way Axis

Metabolic syndrome (MetSyn) is a precursor for several cardiometabolic diseases such as obesity, type-2 diabetes mellitus (T2DM), and cardiovascular diseases. Emerging evidence suggests that vitamin D deficiency links to cardiometabolic diseases through microbiota. A combination of poor vitamin D status and dysbiosis may contribute to the progression of cardiometabolic diseases. Therefore, in this review, we present the relationship among vitamin D, microbiota, and cardiometabolic diseases with a focus on MetSyn. We searched major databases for reports on vitamin D, microbiota, and MetSyn until June 2022. We reviewed 13 reports on the relation between vitamin D and MetSyn (6 randomized controlled and 7 cross-sectional studies) and 6 reports on the effect of vitamin D on the gut microbiome. Adequate vitamin D status has a beneficial effect on gut microbiota, therefore preventing the progression of MetSyn. Further, well-controlled studies are needed for a better understanding of the mechanisms of action involving vitamin D and microbiota in the pathogenesis of cardiometabolic diseases.

Obesity and type 2 diabetes mellitus: connections in epidemiology, pathogenesis, and treatments

The prevalence of obesity and diabetes mellitus (DM) has been consistently increasing worldwide. Sharing powerful genetic and environmental features in their pathogenesis, obesity amplifies the impact of genetic susceptibility and environmental factors on DM. The ectopic expansion of adipose tissue and excessive accumulation of certain nutrients and metabolites sabotage the metabolic balance via insulin resistance, dysfunctional autophagy, and microbiome-gut-brain axis, further exacerbating the dysregulation of immunometabolism through low-grade systemic inflammation, leading to an accelerated loss of functional β-cells and gradual elevation of blood glucose. Given these intricate connections, most available treatments of obesity and type 2 DM (T2DM) have a mutual effect on each other. For example, anti-obesity drugs can be anti-diabetic to some extent, and some anti-diabetic medicines, in contrast, have been shown to increase body weight, such as insulin. Meanwhile, surgical procedures, especially bariatric surgery, are more effective for both obesity and T2DM. Besides guaranteeing the availability and accessibility of all the available diagnostic and therapeutic tools, more clinical and experimental investigations on the pathogenesis of these two diseases are warranted to improve the efficacy and safety of the available and newly developed treatments.

Rapid growth of antimicrobial resistance: the role of agriculture in the problem and the solutions

Abstract

The control of infectious diseases has always been a top medical priority. For years during the so-called antibiotic era, we enjoyed prolonged life expectancy and the benefits of superior pathogen control. The devastating failure of the medical system, agriculture and pharmaceutical companies and the general population to appreciate and safeguard these benefits is now leading us into a grim post-antibiotic era. Antimicrobial resistance (AMR) refers to microorganisms becoming resistant to antibiotics that were designed and expected to kill them. Prior to the COVID-19 pandemic, AMR was recognised by the World Health Organization as the central priority area with growing public awareness of the threat AMR now presents. The Review on Antimicrobial Resistance, a project commissioned by the UK government, predicted that the death toll of AMR could be one person every 3 seconds, amounting to 10 million deaths per year by 2050. This review aims to raise awareness of the evergrowing extensiveness of antimicrobial resistance and identify major sources of this adversity, focusing on agriculture’s role in this problem and its solutions.

Keypoints

• Widespread development of antibiotic resistance is a major global health risk.

• Antibiotic resistance is abundant in agricultural produce, soil, food, water, air and probiotics.

• New approaches are being developed to control and reduce antimicrobial resistance.

Analysis of the blood bacterial composition of patients with acute coronary syndrome and chronic coronary syndrome

Emerging evidence revealed that the blood microbiota plays a role in several non-communicable diseases, including cardiovascular disease. However, the role of circulating microbes in atherosclerosis remains understudied. To test this hypothesis, we performed this study to investigate the microbial profile in the blood of Chines atherosclerosis volunteers. A total of seventy Acute Coronary Syndrome patients, seventy Chronic Coronary Syndrome patients, and seventy healthy individuals were examined using high-throughput Illumina Novaseq targeting the V3-V4 regions of the 16S rRNA gene. The relationship between atherosclerosis and blood microbiome, clinical variables, and their functional pathways were also investigated. Our study observed significantly higher alpha diversity indices (Chao1, p = 0.001, and Shannon, p = 0.004) in the acute coronary syndrome group compared with chronic coronary syndrome and healthy group, although a significantly lower alpha diversity was observed in the chronic coronary syndrome compared to acute coronary syndrome and healthy group. Beta diversity based on principal coordinate analysis demonstrated a major separation among the three groups. In addition, using linear discriminant analysis, a significant distinct taxon such as Actinobacteria _ phylum, and Staphylococcus_ genus in the healthy group; Firmicutes_ phylum, and Lactobacillus_ genus in the chronic coronary syndrome group, and Proteobacteria and Acidobacteriota _ phyla in acute coronary syndrome group were observed among three groups. Clusters of Orthologous Genes grouped and Kyoto Encyclopedia of Genes and Genomes pathways suggested a significant variation among all groups (p < 0.05). The blood microbiota analysis provides potential biomarkers for the detection of coronary syndromes in this population.

Human circulating bacteria and dysbiosis in non-infectious diseases

Blood microorganisms were once thought to indicate infection. Blood in healthy people appears to be devoid of growing bacteria; nonetheless, intracellular dormant forms of bacteria have been reported previously. With breakthroughs in sequencing and bioinformatics, the presence of bacterial DNA in healthy human blood initiated the controversy of human blood microbiota (HBM). Recently, bacteria-specific DNA and culturable bacteria were found in healthy human blood. Researchers wanted to study the phenomena of a "healthy blood microbiota" by providing a thorough description of bacterially produced nucleic acids using many complementing molecular and traditional microbiological approaches. Because blood is a relatively limited and particular environment, culturability and plate count issues can be overcome using enhanced cultured procedures. However, more evidence is required to confirm that healthy human blood contains normal microbiota. Cavities, mouth and intestinal microbiota, trauma, surgery, and animal/insect bites can introduce bacteria into human blood. All these factors strengthen the concept of transient blood bacteria too. The presence of blood bacteria may be caused by temporary immunological clearance and absorption by dendritic or M cells. This review provides an extensive and comprehensive analysis that suggests that healthy blood bacteria may not be typical microbiota but transient circulatory microorganisms. In this study, we look at how contaminants (Escherichia, Shigella, Pseudomonads, etc.) from the skin, laboratory environments, and reagents can affect the interpretation of blood-derived microbial information and the relationship between the circulating bacteria and non-communicable diseases. Circulating transient bacteria may play a role in the pathogenesis of non-infectious diseases such as diabetes and CVD. Contamination-free hematological studies can aid in understanding the disease mechanisms, therapy, and biomarkers.

Gram-selective antibacterial peptide hydrogels

The human microbiome plays fundamental roles in human health and disease. However, widely used broad-spectrum antibiotics severely disrupt human-related microbial communities, eventually leading to resistant bacteria, posing a growing threat to global medical health. Antimicrobial peptides (AMPs) are promising antimicrobial agents that barely cause bacterial resistance. Excellent broad-spectrum antimicrobial activities have been achieved using hydrogels self-assembled from AMPs, but there is still a lack of AMP hydrogels that can target Gram-positive and Gram-negative bacteria. Herein, several hydrogels self-assembled from AMPs, termed IK1, IK3, and IK4, were designed and synthesized. In vitro antibacterial results indicated that the IK1 and IK4 hydrogels specifically targeted Gram-positive and Gram-negative bacteria, respectively, while the IK3 hydrogel targeted both Gram-positive and Gram-negative bacteria. The desired broad-spectrum or Gram-selective AMP hydrogels are believed to be obtained through the rational design of the hydrophilicity, hydrophobicity, and charge properties of the peptide molecules. Good in vivo Gram-selective antibacterial properties and the ability to promote wound healing have been demonstrated via treating mouse wound models with these AMP hydrogels. We believe that these Gram-selective AMP hydrogels could potentially have important applications in treating common recurring infections.

Gut microbiota diversity in middle-aged and elderly patients with end-stage diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD), but the mechanism between DKD and ESRD remains unclear. Some experts have put forward the "microbial-centered ESRD development theory", believing that the bacterial load caused by gut microecological imbalance and uremia toxin transfer are the core pathogenic links. The purpose of this study was to analyze the genomic characteristics of gut microbiota in patients with ESRD, specifically DKD or non-diabetic kidney disease (NDKD).

METHODS

In this cross-sectional study, patients with ESRD were recruited in a community, including 22 DKD patients and 22 NDKD patients matched using gender and age. Fecal samples of patients were collected for 16S rDNA sequencing and gut microbiota analysis. The distribution structure, diversity, and abundance of microflora in DKD patients were analyzed by constructing species evolutionary trees and analyzing alpha diversity, beta diversity, and linear discriminant analysis effect size (LEfSe).

RESULTS

The results of our study showed that there were statistically significant differences in the richness and species of gut microbiota at the total level between DKD patients and NDKD patients. The analysis of genus level between the two groups showed significant differences in 16 bacterial genera. Among them, Oscillibacter, Bilophila, UBA1819, Ruminococcaceae UCG-004, Anaerotruncus, Ruminococcaceae, and Ruminococcaceae NK4A214 bacteria in DKD patients were higher than those in NDKD patients.

CONCLUSIONS

16S rDNA sequencing technology was used in this study to analyze the characteristics of intestinal flora in ESRD patients with or without diabetes. We found that there was a significant difference in the intestinal flora of ESRD patients caused by DKD and NDKD, suggesting that these may be potential causative bacteria for the development of ERSD in DKD patients.

Human Blood Bacteriome: Eubiotic and Dysbiotic States in Health and Diseases

The human gut microbiome is acknowledged as being associated with homeostasis and the pathogenesis of several diseases. Conventional culture techniques are limited in that they cannot culture the commensals; however, next-generation sequencing has facilitated the discovery of the diverse and delicate microbial relationship in body sites and blood. Increasing evidence regarding the blood microbiome has revolutionized the concept of sterility and germ theory in circulation. Among the types of microbial communities in the blood, bacteriomes associated with many health conditions have been thoroughly investigated. Blood bacterial profiles in healthy subjects are identified as the eubiotic blood bacteriome, whereas the dysbiotic blood bacteriome represents the change in bacterial characteristics in subjects with diseases showing deviations from the eubiotic profiles. The blood bacterial characteristics in each study are heterogeneous; thus, the association between eubiotic and dysbiotic blood bacteriomes and health and disease is still debatable. Thereby, this review aims to summarize and discuss the evidence concerning eubiotic and dysbiotic blood bacteriomes characterized by next-generation sequencing in human studies. Knowledge pertaining to the blood bacteriome will transform the concepts around health and disease in humans, facilitating clinical implementation in the near future.

Whole-Genome Sequencing Reveals Age-Specific Changes in the Human Blood Microbiota

Based on several reports that indicate the presence of blood microbiota in patients with diseases, we became interested in identifying the presence of bacteria in the blood of healthy individuals. Using 37 samples from 5 families, we extracted sequences that were not mapped to the human reference genome and mapped them to the bacterial reference genome for characterization. Proteobacteria account for more than 95% of the blood microbiota. The results of clustering by means of principal component analysis showed similar patterns for each age group. We observed that the class Gammaproteobacteria was significantly higher in the elderly group (over 60 years old), whereas the arcsine square root-transformed relative abundance of the classes Alphaproteobacteria, Deltaproteobacteria, and Clostridia was significantly lower (p < 0.05). In addition, the diversity among the groups showed a significant difference (p < 0.05) in the elderly group. This result provides meaningful evidence of a consistent phenomenon that chronic diseases associated with aging are accompanied by metabolic endotoxemia and chronic inflammation.

Comparison of Microbial Populations in the Blood of Patients With Myocardial Infarction and Healthy Individuals

Increased bacterial translocation in the gut and bloodstream infections are both major comorbidities of heart failure and myocardial infarction (MI). However, the alterations in the microbiome of the blood of patients with MI remain unclear. To test this hypothesis, we conducted this case-control study to explore the microbiota compositions in the blood of Chinese patients with MI. Using high-throughput Illumina HiSeq sequencing targeting the V3–V4 region of the 16S ribosomal RNA (rRNA) gene, the microbiota communities in the blood of 29 patients with MI and 29 healthy controls were examined. In addition, the relationship between the blood microbiome and clinical features of MI was investigated. This study revealed a significant reduction in alpha diversity (Shannon index) in the MI group compared with the healthy controls. Also, a significant difference was detected in the structure and richness between the patients with MI and healthy controls. The members of the phylum Actinobacteria, class Actinobacteria, order Bifdobacteriales, family Bifidobacteriaceae, and genus Bifidobacterium were significantly abundant in the MI group, while the members of the phylum Bacteroidetes, class Bacteroidia, and order Bacteroidales were significantly enriched in the healthy controls (p < 0.05). Moreover, the functional analysis revealed a significant variation between both groups. For instance, the enrichment of genes involved in the metabolism pathways of three amino acids decreased, that is, nucleotide transport and metabolism, coenzyme transport and metabolism, and lipid transport and metabolism, among others. Our study will contribute to a better knowledge of the microbiota of blood, which will further lead to improved MI diagnosis and therapy. Further study is needed to determine the role of the blood microbiota in human health and disease.

Circulating Microbiota in Cardiometabolic Disease

The rapid expansion of microbiota research has significantly advanced our understanding of the complex interactions between gut microbiota and cardiovascular, metabolic, and renal system regulation. Low-grade chronic inflammation has long been implicated as one of the key mechanisms underlying cardiometabolic disease risk and progression, even before the insights provided by gut microbiota research in the past decade. Microbial translocation into the bloodstream can occur via different routes, including through the oral and/or intestinal mucosa, and may contribute to chronic inflammation in cardiometabolic disease. Among several gut-derived products identifiable in the systemic circulation, bacterial endotoxins and metabolites have been extensively studied, however recent advances in microbial DNA sequencing have further allowed us to identify highly diverse communities of microorganisms in the bloodstream from an -omics standpoint, which is termed "circulating microbiota." While detecting microorganisms in the bloodstream was historically considered as an indication of infection, evidence on the circulating microbiota is continually accumulating in various patient populations without clinical signs of infection and even in otherwise healthy individuals. Moreover, both quantitative and compositional alterations of the circulating microbiota have recently been implicated in the pathogenesis of chronic inflammatory conditions, potentially through their immunostimulatory, atherogenic, and cardiotoxic properties. In this mini review, we aim to provide recent evidence on the characteristics and roles of circulating microbiota in several cardiometabolic diseases, such as type 2 diabetes, cardiovascular disease, and chronic kidney disease, with highlights of our emerging findings on circulating microbiota in patients with end-stage kidney disease undergoing hemodialysis.

New Paradigms for Familiar Diseases: Lessons Learned on Circulatory Bacterial Signatures in Cardiometabolic Diseases

Despite the strongly accumulating evidence for microbial signatures in metabolic tissues, including the blood, suggesting a novel paradigm for metabolic disease development, the notion of a core blood bacterial signature in health and disease remains a contentious concept. Recent studies clearly demonstrate that under a strict contamination-free environment, methods such as 16 S rRNA gene sequencing, fluorescence in-situ hybridization, transmission electron microscopy, and several more, allied with advanced bioinformatics tools, allow unambiguous detection and quantification of bacteria and bacterial DNA in human tissues. Bacterial load and compositional changes in the blood have been reported for numerous disease states, suggesting that bacteria and their components may partially induce systemic inflammation in cardiometabolic disease. This concept has been so far primarily based on measurements of surrogate parameters. It is now highly desirable to translate the current knowledge into diagnostic, prognostic, and therapeutic approaches.This review addresses the potential clinical relevance of a blood bacterial signature pertinent to cardiometabolic diseases and outcomes and new avenues for translational approaches. It discusses pitfalls related to research in low bacterial biomass while proposing mitigation strategies for future research and application approaches.

Deciphering mechanisms and implications of bacterial translocation in human health and disease

Significant increases in potential microbial translocation, especially along the oral-gut axis, have been identified in many immune-related and inflammatory diseases, such as inflammatory bowel disease, colorectal cancer, rheumatoid arthritis, and liver cirrhosis, for which we currently have no cure or long-term treatment options. Recent advances in computational and experimental omics approaches now enable strain tracking, functional profiling, and strain isolation in unprecedented detail, which has the potential to elucidate the causes and consequences of microbial translocation. In this review, we discuss current evidence for the detection of bacterial translocation, examine different translocation axes with a primary focus on the oral-gut axis, and outline currently known translocation mechanisms and how they adversely affect the host in disease. Finally, we conclude with an overview of state-of-the-art computational and experimental tools for strain tracking and highlight the required next steps to elucidate the role of bacterial translocation in human health.

Association of the Microbiota and Pancreatic Cancer: Opportunities and Limitations

The human body is thoroughly colonized by a wide variety of microorganisms, termed microbiota. Pancreatic cancer, one of the most aggressive forms of cancer, is no exception. The microbiota of pancreatic cancer largely influences and even dominates the occurrence, development and outcome of pancreatic cancer in many ways. Studies have shown that microbiota could change the malignant phenotype and prognosis of pancreatic cancer by stimulating persistent inflammation, regulating the antitumor immune system, changing the tumor microenvironment and affecting cellular metabolism. This is why the association of the microbiota with pancreatic cancer is an emerging area of research that warrants further exploration. Herein, we investigated the potential microbial markers of pancreatic cancer, related research models, the mechanism of action of microbiota in pancreatic cancer, and pancreatic cancer-microbiota-related treatment.

Diabetogenically beneficial gut microbiota alterations in third trimester of pregnancy

Altered gut microbiota (dysbiosis), inflammation and weight gain are pivotal to the success of normal pregnancy. These are features of metabolic syndrome that ordinarily increase the risk of type 2 diabetes in non-pregnant individuals. Though gut microbiota influences host energy metabolism and homeostasis, the outcome (healthy or unhealthy) varies depending on pregnancy status. In a healthy pregnancy, the gut microbiota is altered to promote metabolic and immunological changes beneficial to the mother and foetus but could connote a disease state in non-pregnant individuals. During the later stages of gestation, metabolic syndrome-like features, that is, obesity-related gut dysbiotic microbiota, increased insulin resistance, and elevated pro-inflammatory cytokines, promote energy storage in adipose tissue for rapid foetal growth and development, and in preparation for energy-consuming processes such as parturition and lactation. The origin of this gestation-associated host–microbial interaction is still elusive. Therefore, this review critically examined the host–microbial interactions in the gastrointestinal tract of pregnant women at late gestation (third trimester) that shift host metabolism in favour of a diabetogenic or metabolic syndrome-like phenotype. Whether the diabetogenic effects of such interactions are indeed beneficial to both mother and foetus was also discussed with plausible mechanistic pathways and associations highlighted.

Intestinal Barrier Function and Immune Homeostasis Are Missing Links in Obesity and Type 2 Diabetes Development

Noncommunicable diseases, such as type 2 diabetes (T2D), place a burden on healthcare systems worldwide. The rising prevalence of obesity, a major risk factor for T2D, is mainly attributed to the adoption of Westernized diets and lifestyle, which cause metabolic dysfunction and insulin resistance. Moreover, diet may also induce changes in the microbiota composition, thereby affecting intestinal immunity. The critical role of intestinal immunity and intestinal barrier function in the development of T2D is increasingly acknowledged, however, limited studies have investigated the link between intestinal function and metabolic disease. In this review, studies reporting specific roles of the intestinal immune system and intestinal epithelial cells (IECs) in metabolic disease are highlighted. Innate chemokine signaling, eosinophils, immunoglobulin A (IgA), T helper (Th) 17 cells and their cytokines were associated with obesity and/or dysregulated glucose homeostasis. Intestinal epithelial cells (IECs) emerged as critical modulators of obesity and glucose homeostasis through their effect on lipopolysaccharide (LPS) signaling and decontamination. Furthermore, IECs create a link between microbial metabolites and whole-body metabolic function. Future in depth studies of the intestinal immune system and IECs may provide new opportunities and targets to develop treatments and prevention strategies for obesity and T2D.

Diabetic Gastroenteropathy: Soothe the Symptoms or Unravel a Cure?

Autonomic neuropathy in patients with diabetes mellitus, and especially complications related to gastrointestinal neuropathy, are often overlooked in the clinic. Diabetic gastroenteropathy affects every segment of the gastrointestinal tract and generates symptoms that may include nausea, early satiety, vomiting, abdominal pain, constipation, and diarrhea. Severe cases can be complicated by weight loss, dehydration, and electrolyte disturbances. The pathophysiology is complex, the diagnostics and treatment options are multidisciplinary, and there is generally a lack of evidence for the treatment options. The aims for this review are first to summarize the pathophysiology and describe possible and expected symptoms and complications.Further, we will try to supply the clinician with a straightforward tool for diagnostics, and then, we shall summarize established treatment options, including diet recommendations, pharmacological and non-pharmacological options. Finally, we will explore the multiple possibilities of novel treatment, looking at medications related to the pathophysiology of neuropathy, other manifestations of autonomic neuropathies, and symptomatic treatment for other gastrointestinal disorders, also including new knowledge of endosurgical and neuromodulatory treatment. The overall goal is to increase awareness and knowledge on this frequent diabetic complication and to provide better tools for diagnosis and treatment. Ultimately, we hope to encourage further research in this field, as there are clear shortcomings in terms of biomarkers, pathophysiology, as well as treatment possibilities. In conclusion, diagnosis and management of diabetic gastroenteropathy are challenging and often require multidisciplinary teams and multimodal therapies. Treatment options are sparse, but new pharmacological, endoscopic, and neuromodulatory techniques have shown promising results in initial studies.

Intestinal Barrier and Permeability in Health, Obesity and NAFLD

The largest surface of the human body exposed to the external environment is the gut. At this level, the intestinal barrier includes luminal microbes, the mucin layer, gastrointestinal motility and secretion, enterocytes, immune cells, gut vascular barrier, and liver barrier. A healthy intestinal barrier is characterized by the selective permeability of nutrients, metabolites, water, and bacterial products, and processes are governed by cellular, neural, immune, and hormonal factors. Disrupted gut permeability (leaky gut syndrome) can represent a predisposing or aggravating condition in obesity and the metabolically associated liver steatosis (nonalcoholic fatty liver disease, NAFLD). In what follows, we describe the morphological-functional features of the intestinal barrier, the role of major modifiers of the intestinal barrier, and discuss the recent evidence pointing to the key role of intestinal permeability in obesity/NAFLD.

Endurance Training in Humans Modulates the Bacterial DNA Signature of Skeletal Muscle

Accumulating evidence supports the existence of a tissue microbiota, which may regulate the physiological function of tissues in normal and pathological states. To gain insight into the regulation of tissue-borne bacteria in physiological conditions, we quantified and sequenced the 16S rRNA gene in aseptically collected skeletal muscle and blood samples from eight healthy male individuals subjected to six weeks of endurance training. Potential contamination bias was evaluated and the taxa profiles of each tissue were established. We detected bacterial DNA in skeletal muscle and blood, with background noise levels of detected bacterial DNA considerably lower in control versus tissue samples. In both muscle and blood, Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes were the most prominent phyla. Endurance training changed the content of resident bacterial DNA in skeletal muscle but not in blood, with Pseudomonas being less abundant, and both Staphylococcus and Acinetobacter being more abundant in muscle after exercise. Our results provide evidence that endurance training specifically remodels the bacterial DNA profile of skeletal muscle in healthy young men. Future investigations may shed light on the physiological impact, if any, of training-induced changes in bacterial DNA in skeletal muscle.

Gut microbiota in nonalcoholic fatty liver diseases with and without type-2 diabetes mellitus

BACKGROUND AND AIMS

The association between nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) is not very well described but gut microbiota composition is mentioned as a risk factor. The present study aimed to characterize the differences of dominant gut microbiota phyla among people with NAFLD as compared to T2DM and control groups.

PATIENTS AND METHODS

The major bacterial phylum of gut microbiota including Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria, and total bacteria of 15 NAFLD patients with T2DM, 15 NAFLD patients without T2DM, 15 patients with T2DM, and 20 healthy control subjects were assessed by a quantitative PCR (qPCR).

RESULTS

NAFLD patients with T2DM had significantly higher BMI, triglyceride level, and total cholesterol level were compared with controls (Pv < 0.05). Bacteroidetes and Firmicutes phyla were significantly low in NAFLD patients with T2DM (Firmicutes, 2.55 ± 2.25, Pv 0/0002 and Bacteroidetes, 1.55 ± 2.29, Pv 0/0007), while the content of Proteobacteria and Actinobacteria was high in NAFLD patients with T2DM group and there were no significant differences between phyla with NAFLD patients with T2DM group (Pv > 0.05). Furthermore, Firmicutes copy number was lower in the separate groups of NAFLD and T2DM as compared to the healthy controls (Pv < 0.05).

CONCLUSIONS

This study performed gut microbiota for the first time among NAFLD and TDM patients separately and together. This investigation indicated that NAFLD patients with T2DM have a different gut composition in comparison to NAFLD, T2DM alone, which could be associated with disease development.

Associations Between Peripheral Blood Microbiome and the Risk of Hypertension

BACKGROUND

Although previous studies have reported the gut microbiome is closely related to hypertension development, whether the change in blood microbiome is associated with the risk of hypertension remains unclear.

METHODS

One hundred and fifty incident hypertension cases and 150 age (± 2 years) and gender (1:1) matched nonhypertension controls included in this nested case-control study were recruited from a prospective cohort study of "135." The composition of the blood microbiome was characterized using bacterial 16S ribosomal RNA gene sequencing. The relative abundance of detected bacteria was converted to a negative logarithm of 10 for the statistical analysis.

RESULTS

Totally, 10,689,961 high-quality sequences were acquired. The Chao1 index of the blood microbiome in nonhypertension controls was significantly higher than in hypertensive group (2,302.08 ± 752.78 vs. 1,598.21 ± 500.88, P < 0.001). Compared with the nonhypertension controls, the relative abundance of Proteobacteria phylum was significantly increased (P < 0.001), whereas the relative abundance of phyla Firmicutes and Bacteroidetes were significantly reduced in the hypertensive cases (P < 0.001 and P = 0.039, respectively). At genus level, the risk of hypertension was directly associated with the relative abundance of Acinetobacter (odds ratio [OR]: 1.43, 95% confidence interval [CI]: 1.01-2.03), Sphingomonas (OR: 1.84, 95% CI: 1.32-2.56), and Staphylococcus (OR: 0.51, 95% CI: 0.36-0.73), respectively. In addition, the relative abundance of Pseudomonas was minor positively correlated with the total cholesterol level. However, the relative Staphylococcus level was minor positively correlated with high-density lipoprotein cholesterol level.

CONCLUSIONS

The composition of the blood microbiome is significantly associated with the development of hypertension.