CRB1-associated retinal degeneration is dependent on bacterial translocation from the gut

The Crumbs homolog 1 (CRB1) gene is associated with retinal degeneration, most commonly Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP). Here, we demonstrate that murine retinas bearing the Rd8 mutation of Crb1 are characterized by the presence of intralesional bacteria. While normal CRB1 expression was enriched in the apical junctional complexes of retinal pigment epithelium and colonic enterocytes, Crb1 mutations dampened its expression at both sites. Consequent impairment of the outer blood retinal barrier and colonic intestinal epithelial barrier in Rd8 mice led to the translocation of intestinal bacteria from the lower gastrointestinal (GI) tract to the retina, resulting in secondary retinal degeneration. Either the depletion of bacteria systemically or the reintroduction of normal Crb1 expression colonically rescued Rd8-mutation-associated retinal degeneration without reversing the retinal barrier breach. Our data elucidate the pathogenesis of Crb1-mutation-associated retinal degenerations and suggest that antimicrobial agents have the potential to treat this devastating blinding disease.

Heart-gut-microbiota communication determines the severity of cardiac injury after myocardial ischemia/reperfusion

BACKGROUND

Recent studies have suggested a key role of intestinal microbiota in pathological progress of multiple organs via immune modulation. However, the interactions between heart and gut microbiota remain to be fully elucidated. The aim of the study is to investigate the role of gut microbiota in post ischemia/reperfusion (I/R) inflammatory microenvironment.

METHODS AND RESULTS

Here, we conducted a case-control study to explore the association of gut bacteria translocation products with inflammation biomarkers and I/R injury severity in STEMI patients. Then, we used a mouse model to determine the effects of myocardial I/R injury on gut microbiota dysbiosis and translocation. Blooming of Proteobacteria was identified as hallmark of post-I/R dysbiosis, which was associated with gut bacteria translocation. Abrogation of gut bacteria translocation by antibiotic cocktail alleviated myocardial I/R injury via mitigating excessive inflammation and attenuating myeloid cells mobilization, indicating the bidirectional heart-gut-microbiome-immune axis in myocardial I/R injury. Glucagon-like peptide 2 (GLP-2), an endocrine peptide produced by intestinal L-cells, was used in experimental myocardial I/R model. GLP-2 administration restored gut microbiota disorder and prevented bacteria translocation, eventually attenuated myocardial I/R injury through alleviating systemic inflammation.

CONCLUSION

Our work identifies a bidirectional communication along the heart-gut-microbiome-immune axis in myocardial I/R injury and demonstrates gut bacteria translocation as a key regulator in amplifying inflammatory injury. Furthermore, our study sheds new light on the application of GLP-2 as a promising therapy targeting gut bacteria translocation in myocardial I/R injury.

TRANSLATIONAL PERSPECTIVE

This study demonstrates a unique bidirectional communication along the heart-gut-microbiome-immune axis in myocardial I/R injury. Myocardial I/R injury induced gut microbiota dysbiosis and gut barrier disruption thus leading to bacterial translocation and these changes in turn aggravated I/R injury by augmenting inflammation. Furthermore, our study sheds new light on the application of GLP-2 as a promising therapy targeting gut bacteria translocation in myocardial I/R injury. These findings highlight the gut microbiota targeting therapy as a potential therapeutics strategy to attenuate myocardial I/R injury and are of great translational value.

Creeping fat formation and interaction with intestinal disease in Crohn's disease

Creeping fat (CrF), also known as fat wrapping, is a significant disease characteristic of Crohn's disease (CD). The transmural inflammation impairs intestinal integrity and facilitates bacteria translocation, aggravating immune response. CrF is a rich source of pro-inflammatory and pro-fibrotic cytokines with complex immune microenvironment. The inflamed and stricturing intestine is often wrapped by CrF, and CrF is associated with greater severity of CD. The large amount of innate and adaptive immune cells as well as adipocytes in CrF promote fibrosis in the affected intestine by secreting large amount of pro-fibrotic cytokines, adipokines, growth factors and fatty acids. CrF is a potential therapeutic target for CD treatment and a promising bio-marker for predicting response to drug therapy. This review aims to summarize and update the clinical manifestation and application of CrF and the underlying molecular mechanism involved in the pathogenesis of intestinal inflammation and fibrosis in CD.

The Gut Microbiota Metabolite Succinate Promotes Adipose Tissue Browning in Crohn's Disease

BACKGROUND AND AIMS

Crohn's disease [CD] is associated with complex microbe-host interactions, involving changes in microbial communities, and gut barrier defects, leading to the translocation of microorganisms to surrounding adipose tissue [AT]. We evaluated the presence of beige AT depots in CD and questioned whether succinate and/or bacterial translocation promotes white-to-beige transition in adipocytes.

METHODS

Visceral [VAT] and subcutaneous [SAT] AT biopsies, serum and plasma were obtained from patients with active [n = 21] or inactive [n = 12] CD, and from healthy controls [n = 15]. Adipose-derived stem cells [ASCs] and AT macrophages [ATMs] were isolated from VAT biopsies.

RESULTS

Plasma succinate levels were significantly higher in patients with active CD than in controls and were intermediate in those with inactive disease. Plasma succinate correlated with the inflammatory marker high-sensitivity C-reactive protein. Expression of the succinate receptor SUCNR1 was higher in VAT, ASCs and ATMs from the active CD group than from the inactive or control groups. Succinate treatment of ASCs elevated the expression of several beige AT markers from controls and from patients with inactive disease, including uncoupling protein-1 [UCP1]. Notably, beige AT markers were prominent in ASCs from patients with active CD. Secretome profiling revealed that ASCs from patients with active disease secrete beige AT-related proteins, and co-culture assays showed that bacteria also trigger the white-to-beige switch of ASCs from patients with CD. Finally, AT depots from patients with CD exhibited a conversion from white to beige AT together with high UCP1 expression, which was corroborated by in situ thermal imaging analysis.

CONCLUSIONS

Succinate and bacteria trigger white-to-beige AT transition in CD. Understanding the role of beige AT in CD might aid in the development of therapeutic or diagnostic interventions.

Preterm Birth Is Correlated With Increased Oral Originated Microbiome in the Gut

Background

Preterm birth is one of the leading causes of perinatal morbidity and mortality. Gut microbiome dysbiosis is closely related to adverse pregnancy outcomes. However, the role of the gut microbiome in the pathogenesis of preterm birth remains poorly studied.

Method

We collected fecal samples from 41 women (cases presenting with threatened preterm labor =19, 11 of which delivered preterm; gestational age-matched no-labor controls, all of which delivered at term = 22) were recruited for the study. We performed 16S rRNA amplicon sequencing to compare the composition of the gut microbiome in threatened preterm labor cases and controls and among women who delivered preterm and at term. By annotating taxonomic biomarkers with the Human Oral Microbiome Database, we observed an increased abundance of potential oral-to-gut bacteria in preterm patients.

Results

Patients with preterm birth showed a distinct gut microbiome dysbiosis compared with those who delivered at term. Opportunistic pathogens, particularly Porphyromonas, Streptococcus, Fusobacterium, and Veillonella, were enriched, whereas Coprococcus and Gemmiger were markedly depleted in the preterm group. Most of the enriched bacteria were annotated oral bacteria using the Human Oral Microbiome Database. These potential oral-to-gut bacteria were correlated with clinical parameters that reflected maternal and fetal status.

Conclusions

This study suggests that patients who deliver preterm demonstrate altered gut microbiome that may contain higher common oral bacteria.

Gut Alterations in Septic Patients: A Biochemical Literature Review

BACKGROUND

Sepsis is a life-threatening organ dysfunction with high mortality and morbidity rate and with the disease progression many alterations are observed in different organs. The gastrointestinal tract is often damaged during sepsis and septic shock and main symptoms are related to increased permeability, bacterial translocation and malabsorption. These intestinal alterations can be both cause and effect of sepsis.

OBJECTIVE

The aim of this review is to analyze different pathways that lead to intestinal alteration in sepsis and to explore the most common methods for intestinal permeability measurement and, at the same time to evaluate if their use permit to identify patients at high risk of sepsis and eventually to estimate the prognosis.

MATERIAL AND METHODS

The peer-reviewed articles analyzed were selected from PubMed databases using the keywords "sepsis" "gut alteration", "bowel permeability", "gut alteration", "bacterial translocation", "gut permeability tests", "gut inflammation". Among the 321 papers identified, 190 articles were selected, after title - abstract examination and removing the duplicates and studies on pediatric population,only 105 articles relating to sepsis and gut alterations were analyzed.

RESULTS

Integrity of the intestinal barrier plays a key role in the preventing of bacterial translocation and gut alteration related to sepsis. It is obvious that this dysfunction of the small intestine can have serious consequences and the early identification of patients at risk - to develop malabsorption or already malnourished - is very recommended to increase the survivor rate. Until now, in critical patients, the dosage of citrullinemia is easily applied test in clinical setting, in fact, it is relatively easy to administer and allows to accurately assess the functionality of enterocytes.

CONCLUSION

The sepsis can have an important impact on the gastrointestinal function. In addition, the alteration of the permeability can become a source of systemic infection. At the moment, biological damage markers are not specific, but the dosage of LPS, citrulline, lactulose/mannitol test, FABP and fecal calprotectin are becoming an excellent alternative with high specificity and sensitivity.

Bacterial DNA content in the intestinal wall from infants with necrotizing enterocolitis

PURPOSE

The objective of our study was to quantify mucosal bacterial DNA within specimens from neonates undergoing small bowel resection for necrotizing enterocolitis (NEC).

METHODS

We obtained clinical information and pathologic specimens from all infants diagnosed with NEC who underwent surgical treatment at our institution from 1999 to 2008. Bacterial and human DNA were isolated from paraffin-embedded surgical specimens, and real time polymerase chain reaction was used to amplify bacterial and human genes. Linear regression was used to quantify the amount of human and bacterial DNA in our specimens.

RESULTS

From a cohort of 50 infants, we identified 23 infants who underwent both surgical resection and subsequent intestinal reanastomosis. Thirteen (59%) of the neonates had Bell stage III NEC, and 9 (41%) had stage II. There was significantly more bacterial DNA in the resection specimens than in the reanastomosis specimens. This corresponds to a median (interquartile range) increase of 1.81 (1.11-4.69)-fold bacterial DNA in the resection specimen compared with the reanastomosis specimen (P < .05).

CONCLUSION

There is more bacterial DNA in infants with acute NEC compared with the same infants after the NEC had clinically resolved. These findings underscore the potential relevance of adherent or invasive bacteria across the bowel wall in the pathogenesis of NEC.