Faecalibacterium prausnitzii-derived microbial anti-inflammatory molecule regulates intestinal integrity in diabetes mellitus mice via modulating tight junction protein expression

A comprehensive review for gut microbes: technologies, interventions, metabolites and diseases

Gut microbes have attracted much more attentions in the recent decade since their essential roles in the development of metabolic diseases, cancer and neurological diseases. Considerable evidence indicates that the metabolism of gut microbes exert influences on intestinal homeostasis and human diseases. Here, we first reviewed two mainstream sequencing technologies involving 16s rRNA sequencing and metagenomic sequencing for gut microbes, and data analysis methods assessing alpha and beta diversity. Next, we introduced some observational studies reflecting that many factors, such as lifestyle and intake of diets, drugs, contribute to gut microbes' quantity and diversity. Then, metabolites produced by gut microbes were presented to understand that gut microbes exert on host homeostasis in the intestinal epithelium and immune system. Finally, we focused on the molecular mechanism of gut microbes on the occurrence and development of several common diseases. In-depth knowledge of the relationship among interventions, gut microbes and diseases might provide new insights in to disease prevention and treatment.

Impaired intestinal barrier function in type 2 diabetic patients measured by serum LPS, Zonulin, and IFABP

INTRODUCTION

The epithelial tight junctions of intestine were impaired in murine model of type 2 diabetes mellitus (T2DM). The aim of this work was to investigate the alteration of intestinal barrier in T2DM patients.

METHODS

90 patients with T2DM and 28 healthy controls were recruited. Serum lipopolysaccharide (LPS), Zonulin, and intestinal fatty acid binding protein (IFABP) were measured by ELISA, based on which a derived permeability risk score (PRS) was calculated. Subgroup analyses were conducted based on the glycemic control (HbA1c < 7%, or HbA1c ≥ 7%), the amount of chronic diabetic complications, and the use of aspirin at the time.

RESULTS

Serum LPS, Zonulin, and IFABP, and PRS of T2DM group were significantly higher than those of the control group (p < 0.05 for all). Serum LPS and PRS was higher in T2DM patients with poor glycemic control (both p < 0.05). Patients with more chronic complications of diabetes had higher serum LPS and IFABP, and PRS (all p < 0.05). No differences were found in these serum markers between T2DM patients being treated with aspirin or not.

CONCLUSIONS

Intestinal barrier function was impaired in T2DM patients. Poor glycemic control and more chronic complications of diabetes were associated with worse intestinal barrier function. Treatment with aspirin did not aggravate the impairment of intestinal barrier in T2DM patients.

Genetic Basis of Tiller Dynamics of Rice Revealed by Genome-Wide Association Studies

A tiller number is the key determinant of rice plant architecture and panicle number and consequently controls grain yield. Thus, it is necessary to optimize the tiller number to achieve the maximum yield in rice. However, comprehensive analyses of the genetic basis of the tiller number, considering the development stage, tiller type, and related traits, are lacking. In this study, we sequence 219 Korean rice accessions and construct a high-quality single nucleotide polymorphism (SNP) dataset. We also evaluate the tiller number at different development stages and heading traits involved in phase transitions. By genome-wide association studies (GWASs), we detected 20 significant association signals for all traits. Five signals were detected in genomic regions near known candidate genes. Most of the candidate genes were involved in the phase transition from vegetative to reproductive growth. In particular, HD1 was simultaneously associated with the productive tiller ratio and heading date, indicating that the photoperiodic heading gene directly controls the productive tiller ratio. Multiple linear regression models of lead SNPs showed coefficients of determination (R²) of 0.49, 0.22, and 0.41 for the tiller number at the maximum tillering stage, productive tiller number, and productive tiller ratio, respectively. Furthermore, the model was validated using independent japonica rice collections, implying that the lead SNPs included in the linear regression model were generally applicable to the tiller number prediction. We revealed the genetic basis of the tiller number in rice plants during growth, By GWASs, and formulated a prediction model by linear regression. Our results improve our understanding of tillering in rice plants and provide a basis for breeding high-yield rice varieties with the optimum the tiller number.

Dysbiosis of Gut Microbiota and Short-Chain Fatty Acids in Encephalitis: A Chinese Pilot Study

Background

Encephalitis, the inflammation of the brain, may be caused by an infection or an autoimmune reaction. However, few researches were focused on the gut microbiome characteristics in encephalitis patients.

Methods

A prospective observational study was conducted in an academic hospital in Guangzhou from February 2017 to February 2018. Patients with encephalitis were recruited. Fecal and serum samples were collected at admission. Healthy volunteers were enrolled from a community. Disease severity scores were recorded by specialized physicians, including Glasgow Coma Scale (GCS), Sequential Organ Failure Assessment (SOFA), and Acute Physiology and Chronic Health Evaluation-II (APACHE-II). 16S rRNA sequence was performed to analyze the gut microbiome, then the α-diversities and β-diversities were estimated. Short-chain fatty acids (SCFAs) were extracted from fecal samples and determined by gas chromatography-mass spectrometry. Serum D-lactate (D-LA), intestinal fatty acid-binding protein (iFABP), lipopolysaccharide (LPS), and lipopolysaccharide-binding protein (LBP) were measured by enzyme-linked immunosorbent assay (ELISA). The associations among microbial indexes and clinical parameters were evaluated by Spearman correlation analysis.

Results

In total, twenty-eight patients were recruited for analysis (median age 46 years; 82.1% male; median GCS 6.5; median SOFA 6.5; median APACHE-II 14.5). Twenty-eight age- and sex-matched healthy subjects were selected as controls. The β-diversities between patients and healthy subjects were significantly different. The α-diversities did not show significant differences between these two groups. In the patient group, the abundances of Bacteroidetes, Proteobacteria, and Bacilli were significantly enriched. Accordingly, fecal SCFA levels were decreased in the patient group, whereas serum D-LA, iFABP, LPS, and LBP levels were increased compared with those in healthy subjects. Correlation analyses showed that disease severity had positive correlations with Proteobacteria and Akkermansia but negative correlations with Firmicutes, Clostridia, and Ruminococcaceae abundances. The cerebrospinal fluid albumin-to-serum albumin ratio (CSAR) was positively related to the α-diversity but negatively correlated with the fecal butyrate concentration.

Conclusion

Gut microbiota disruption was observed in encephalitis patients, which manifested as pathogen dominance and health-promoting commensal depletion. Disease severity and brain damage may have associations with the gut microbiota or its metabolites. The causal relationship should be further explored in future studies.

The Effects of Type 2 Diabetes Mellitus on Organ Metabolism and the Immune System

Metabolic abnormalities such as dyslipidemia, hyperinsulinemia, or insulin resistance and obesity play key roles in the induction and progression of type 2 diabetes mellitus (T2DM). The field of immunometabolism implies a bidirectional link between the immune system and metabolism, in which inflammation plays an essential role in the promotion of metabolic abnormalities (e.g., obesity and T2DM), and metabolic factors, in turn, regulate immune cell functions. Obesity as the main inducer of a systemic low-level inflammation is a main susceptibility factor for T2DM. Obesity-related immune cell infiltration, inflammation, and increased oxidative stress promote metabolic impairments in the insulin-sensitive tissues and finally, insulin resistance, organ failure, and premature aging occur. Hyperglycemia and the subsequent inflammation are the main causes of micro- and macroangiopathies in the circulatory system. They also promote the gut microbiota dysbiosis, increased intestinal permeability, and fatty liver disease. The impaired immune system together with metabolic imbalance also increases the susceptibility of patients to several pathogenic agents such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Thus, the need for a proper immunization protocol among such patients is granted. The focus of the current review is to explore metabolic and immunological abnormalities affecting several organs of T2DM patients and explain the mechanisms, whereby diabetic patients become more susceptible to infectious diseases.

Faecalibacterium prausnitzii-derived microbial anti-inflammatory molecule regulates intestinal integrity in diabetes mellitus mice via modulating tight junction protein expression

BACKGROUND

Impaired intestinal barrier structure and function have been validated as an important pathogenic process in type 2 diabetes mellitus (T2DM). Gut dysbiosis is thought to be the critical factor in diabetic intestinal pathogenesis. As the most abundant commensal bacteria, Faecalibacterium prausnitzii (F. prausnitzii) play important roles in gut homeostasis. The microbial anti-inflammatory molecule (MAM), an F. prausnitzii metabolite, has anti-inflammatory potential in inflammatory bowel disease (IBD). Thus, we aimed to explore the function and mechanism of MAM on the diabetic intestinal epithelium.

METHODS

16S high-throughput sequencing was used to analyze the gut microbiota of db/db mice (T2DM mouse model). We transfected a FLAG-tagged MAM plasmid into human colonic cells to explore the protein-protein interactions and observe cell monolayer permeability. For in vivo experiments, db/db mice were supplemented with recombinant His-tagged MAM protein from E. coli BL21 (DE3).

RESULTS

The abundance of F. prausnitzii was downregulated in the gut microbiota of db/db mice. Immunoprecipitation (IP) and mass spectroscopy (MS) analyses revealed that MAM potentially interacts with proteins in the tight junction pathway, including zona occludens 1 (ZO-1). FLAG-tagged MAM plasmid transfection stabilized the cell permeability and increased ZO-1 expression in NCM460, Caco2, and HT-29 cells. The db/db mice supplemented with recombinant His-tagged MAM protein showed restored intestinal barrier function and elevated ZO-1 expression.

CONCLUSIONS

Our study shows that MAM from F. prausnitzii can restore the intestinal barrier structure and function in DM conditions via the regulation of the tight junction pathway and ZO-1 expression.

Disruption of tight junction structure contributes to secretory dysfunction in IgG4-related sialadenitis

IgG4-related sialadenitis (IgG4-RS) is a chronic fibro-inflammatory disease characterized by swelling of salivary glands and varying degrees of xerostomia. Tight junctions (TJs) play an essential role in maintaining secretory function by regulating the paracellular flow of ions and water. However, whether TJs are altered and contribute to the hyposecretion in IgG4-RS is not fully understood. Here, a total of 399 differentially expressed proteins were identified in IgG4-RS submandibular glands (SMGs) and enriched in the regulation of actin cytoskeleton and the salivary secretion. Real-time PCR results showed that the mRNA levels of claudin-3, -4, -6, -7, -8, -10, -12, occludin, and ZO-1 were significantly lower, whereas claudin-1 and -5 were higher in IgG4-RS SMGs. Immunohistochemical and immunofluorescence staining revealed that claudin-1, -3, -4, occludin, and ZO-1 were mainly distributed at apicolateral membranes in acini and ducts of SMGs from controls, whereas claudin-1 protein intensity at apicolateral membrane was elevated, while the staining of claudin-3, -4, and ZO-1 were reduced in IgG4-RS SMGs. Occludin was dispersed into cytoplasm of acini and ducts in SMGs of patients. Among them, claudin-3 and ZO-1 protein levels were positively correlated with saliva flow rate. Furthermore, the decreased fluorescence intensity of F-actin at peri-apicolateral membranes and the loss of ZO-1 staining at the same location were observed in acinar and ductal cells of IgG4-RS SMGs, which might be responsible for disorganization of TJ complex. Taken together, these findings indicate that the integrity of TJ complex of SMGs is impaired and might contribute to hyposalivation of IgG4-RS patients.